Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of carbon-based compounds, hydrocarbons, and their derivatives. These compounds may contain any number of other elements, including hydrogen, nitrogen, oxygen, the halogens as well as phosphorus, silicon, and sulfur.[1][2][3]
Organic compounds form the basis of almost all earthly life processes (with very few exceptions). They are structurally diverse. The range of application of organic compounds is enormous. They either form the basis of, or are important constituents of, many products including plastics, drugs, petrochemicals, food, explosives, and paints.

Before the nineteenth century, chemists generally believed that compounds obtained from living organisms were too complex to be synthesized. According to the concept of vitalism, organic matter was endowed with a "vital force". They named these compounds "organic" and directed their investigations toward inorganic materials that seemed more easily studied.[citation needed]
During the first half of the nineteenth century, scientists realized that organic compounds can be synthesized in the laboratory. Around 1816 Michel Chevreul started a study of soaps made from various fats and alkalis. He separated the different acids that, in combination with the alkali, produced the soap. Since these were all individual compounds, he demonstrated that it was possible to make a chemical change in various fats (which traditionally come from organic sources), producing new compounds, without "vital force". In 1828 Friedrich Wöhler produced the organic chemical urea (carbamide), a constituent of urine, from the inorganic ammonium cyanate NH4CNO, in what is now called the Wöhler synthesis. Although Wöhler was always cautious about claiming that he had disproved the theory of vital force, this event has often been thought of as a turning point.[citation needed]
In 1856 William Henry Perkin, while trying to manufacture quinine, accidentally manufactured the organic dye now known as Perkin's mauve.[citation needed] Through its great financial success, this discovery greatly increased interest in organic chemistry.
The crucial breakthrough for organic chemistry was the concept of chemical structure, developed independently and simultaneously by Friedrich August Kekulé and Archibald Scott Couper in 1858.[citation needed] Both men suggested that tetravalent carbon atoms could link to each other to form a carbon lattice, and that the detailed patterns of atomic bonding could be discerned by skillful interpretations of appropriate chemical reactions.
The history of organic chemistry continued with the discovery of petroleum and its separation into fractions according to boiling ranges. The conversion of different compound types or individual compounds by various chemical processes created the petroleum chemistry leading to the birth of the petrochemical industry, which successfully manufactured artificial rubbers, the various organic adhesives, the property-modifying petroleum additives, and plastics.
The pharmaceutical industry began in the last decade of the 19th century when the manufacturing of acetylsalicylic acid (more commonly referred to as aspirin) in Germany was started by Bayer.[citation needed] The first time a drug was systematically improved was with arsphenamine (Salvarsan). Though numerous derivatives of the dangerous toxic atoxyl were examined by Paul Ehrlich and his group, the compound with best effectiveness and toxicity characteristics was selected for production.[citation needed]
Although early examples of organic reactions and applications were often serendipitous, the latter half of the 19th century witnessed highly systematic studies of organic compounds.[citation needed] Beginning in the 20th century, progress of organic chemistry allowed the synthesis of highly complex molecules via multistep procedures.[citation needed] Concurrently, polymers and enzymes were understood to be large organic molecules, and petroleum was shown to be of biological origin. The process of finding new synthesis routes for a given compound is called total synthesis. Total synthesis of complex natural compounds started with urea, and increased in complexity to glucose and terpineol. In 1907, total synthesis was commercialized for the first time by Gustaf Komppa with camphor.[citation needed] Pharmaceutical benefits have been substantial.[citation needed] For example, cholesterol-related compounds have opened ways to synthesis complex human hormones and their modified derivatives. Since the start of the 20th century, complexity of total syntheses has been increasing, with examples such as lysergic acid and vitamin B12.[citation needed]
Biochemistry has only started in the 20th century, opening up a new chapter of organic chemistry with enormous scope. Biochemistry, like organic chemistry, primarily focuses on compounds containing carbon.[citation needed]
[edit]Characterization

Since organic compounds often exist as mixtures, a variety of techniques have also been developed to assess purity, especially important being chromatography techniques such as HPLC and gas chromatography. Traditional methods of separation include distillation, crystallization, and solvent extraction.
Organic compounds were traditionally characterized by a variety of chemical tests, called "wet methods", but such tests have been largely displaced by spectroscopic or other computer-intensive methods of analysis.[4] Listed in approximate order of utility, the chief analytical methods are:
Nuclear magnetic resonance (NMR) spectroscopy is the most commonly used technique, often permitting complete assignment of atom connectivity and even stereochemistry using correlation spectroscopy. The principal constituent atoms of organic chemistry - hydrogen and carbon - exist naturally with NMR-responsive isotopes, respectively 1H and 13C.
Elemental analysis: A destructive method used to determine the elemental composition of a molecule. See also mass spectrometry, below.
Mass spectrometry indicates the molecular weight of a compound and, from the fragmentation patterns, its structure. High resolution mass spectrometry can usually identify the exact formula of a compound and is used in lieu of elemental analysis. In former times, mass spectrometry was restricted to neutral molecules exhibiting some volatility, but advanced ionization techniques allow one to obtain the "mass spec" of virtually any organic compound.
Crystallography is an unambiguous method for determining molecular geometry, the proviso being that single crystals of the material must be available and the crystal must be representative of the sample. Highly automated software allows a structure to be determined within hours of obtaining a suitable crystal.
Traditional spectroscopic methods such as infrared spectroscopy, optical rotation, UV/VIS spectroscopy provide relatively nonspecific structural information but remain in use for specific classes of compounds.
[edit]Properties

Physical properties of organic compounds typically of interest include both quantitative and qualitative features. Quantitative information includes melting point, boiling point, and index of refraction. Qualitative properties include odor, consistency, solubility, and color.
[edit]Melting and boiling properties
In contrast to many inorganic materials, organic compounds typically melt and many boil. In earlier times, the melting point (m.p.) and boiling point (b.p.) provided crucial information on the purity and identity of organic compounds. The melting and boiling points correlate with the polarity of the molecules and their molecular weight. Some organic compounds, especially symmetrical ones, sublime, that is they evaporate without melting. A well known example of a sublimable organic compound is para-dichlorobenzene, the odiferous constituent of modern mothballs. Organic compounds are usually not very stable at temperatures above 300 °C, although some exceptions exist.
[edit]Solubility
Neutral organic compounds tend to be hydrophobic, that is they are less soluble in water than in organic solvents. Exceptions include organic compounds that contain ionizable groups as well as low molecular weight alcohols, amines, and carboxylic acids where hydrogen bonding occurs. Organic compounds tend to dissolve in organic solvents. Solvents can be either pure substances like ether or ethyl alcohol, or mixtures, such as the paraffinic solvents such as the various petroleum ethers and white spirits, or the range of pure or mixed aromatic solvents obtained from petroleum or tar fractions by physical separation or by chemical conversion. Solubility in the different solvents depends upon the solvent type and on the functional groups if present.
[edit]Solid state properties
Various specialized properties of molecular crystals and organic polymers with conjugated systems are of interest depending on applications, e.g. thermo-mechanical and electro-mechanical such as piezoelectricity, electrical conductivity (see conductive polymers and organic semiconductors), and electro-optical (e.g. non-linear optics) properties. For historical reasons, such properties are mainly the subjects of the areas of po

Inorganic chemistry

Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds (carbon based compounds, usually containing C-H bonds), which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, and there is much overlap, most importantly in the sub-discipline of organometallic chemistry.

Many inorganic compounds are ionic compounds, consisting of cations and anions joined by ionic bonding. Examples of salts (which are ionic compounds) are magnesium chloride MgCl2, which consists of magnesium cations Mg2+ and chloride anions Cl−; or sodium oxide Na2O, which consists of sodium cations Na+ and oxide anions O2−. In any salt, the proportions of the ions are such that the electric charges cancel out, so that the bulk compound is electrically neutral. The ions are described by their oxidation state and their ease of formation can be inferred from the ionization potential (for cations) or from the electron affinity (anions) of the parent elements.
Important classes of inorganic salts are the oxides, the carbonates, the sulfates and the halides. Many inorganic compounds are characterized by high melting points. Inorganic salts typically are poor conductors in the solid state. Another important feature is their solubility in water e.g. (see: solubility chart), and ease of crystallization. Where some salts (e.g. NaCl) are very soluble in water, others (e.g. SiO2) are not.
The simplest inorganic reaction is double displacement when in mixing of two salts the ions are swapped without a change in oxidation state. In redox reactions one reactant, the oxidant, lowers its oxidation state and another reactant, the reductant, has its oxidation state increased. The net result is an exchange of electrons. Electron exchange can occur indirectly as well, e.g. in batteries, a key concept in electrochemistry.
When one reactant contains hydrogen atoms, a reaction can take place by exchanging protons in acid-base chemistry. In a more general definition, an acid can be any chemical species capable of binding to electron pairs is called a Lewis acid; conversely any molecule that tends to donate an electron pair is referred to as a Lewis base. As a refinement of acid-base interactions, the HSAB theory takes into account polarizability and size of ions.
Inorganic compounds are found in nature as minerals. Soil may contain iron sulfide as pyrite or calcium sulfate as gypsum. Inorganic compounds are also found multitasking as biomolecules: as electrolytes (sodium chloride), in energy storage (ATP) or in construction (the polyphosphate backbone in DNA).
The first important man-made inorganic compound was ammonium nitrate for soil fertilization through the Haber process. Inorganic compounds are synthesized for use as catalysts such as vanadium(V) oxide and titanium(III) chloride, or as reagents in organic chemistry such as lithium aluminium hydride.
Subdivisions of inorganic chemistry are organometallic chemistry, cluster chemistry and bioinorganic chemistry. These fields are active areas of research in inorganic chemistry, aimed toward new catalysts, superconductors, and therapies.
[edit]Industrial inorganic chemistry
Inorganic chemistry is a highly practical area of science. Traditionally, the scale of a nation's economy could be evaluated by their productivity of sulfuric acid. The top 20 inorganic chemicals manufactured in Canada, China, Europe, India, Japan, and the US (2005 data):[1] aluminium sulfate, ammonia, ammonium nitrate, ammonium sulfate, carbon black, chlorine, hydrochloric acid, hydrogen, hydrogen peroxide, nitric acid, nitrogen, oxygen, phosphoric acid, sodium carbonate, sodium chlorate, sodium hydroxide, sodium silicate, sodium sulfate, sulfuric acid, and titanium dioxide.
The manufacturing of fertilizers is another practical application of industrial inorganic chemistry.

Energy

In physics, energy (Ancient Greek: ἐνέργεια energeia "activity, operation"[1]) is an indirectly observed quantity that is often understood as the ability of a physical system to do work on other physical systems.[2][3] Since work is defined as a force acting through a distance (a length of space), energy is always equivalent to the ability to exert pulls or pushes against the basic forces of nature, along a path of a certain length.
The total energy contained in an object is identified with its mass, and energy cannot be created or destroyed. When matter (ordinary material particles) is changed into energy (such as energy of motion, or into radiation), the mass of the system does not change through the transformation process. However, there may be mechanistic limits as to how much of the matter in an object may be changed into other types of energy and thus into work, on other systems. Energy, like mass, is a scalar physical quantity. In the International System of Units (SI), energy is measured in joules, but in many fields other units, such as kilowatt-hours and kilocalories, are customary. All of these units translate to units of work, which is always defined in terms of forces and the distances that the forces act through.
A system can transfer energy to another system by simply transferring matter to it (since matter is equivalent to energy, in accordance with its mass). However, when energy is transferred by means other than matter-transfer, the transfer produces changes in the second system, as a result of work done on it. This work manifests itself as the effect of force(s) applied through distances within the target system. For example, a system can emit energy to another by transferring (radiating) electromagnetic energy, but this creates forces upon the particles that absorb the radiation. Similarly, a system may transfer energy to another by physically impacting it, but in that case the energy of motion in an object, called kinetic energy, results in forces acting over distances (new energy) to appear in another object that is struck. Transfer of thermal energy by heat occurs by both of these mechanisms: heat can be transferred by electromagnetic radiation, or by physical contact in which direct particle-particle impacts transfer kinetic energy.
Energy may be stored in systems without being present as matter, or as kinetic or electromagnetic energy. Stored energy is created whenever a particle has been moved through a field it interacts with (requiring a force to do so), but the energy to accomplish this is stored as a new position of the particles in the field—a configuration that must be "held" or fixed by a different type of force (otherwise, the new configuration would resolve itself by the field pushing or pulling the particle back toward its previous position). This type of energy "stored" by force-fields and particles that have been forced into a new physical configuration in the field by doing work on them by another system, is referred to as potential energy. A simple example of potential energy is the work needed to lift an object in a gravity field, up to a support. Each of the basic forces of nature is associated with a different type of potential energy, and all types of potential energy (like all other types of energy) appears as system mass, whenever present. For example, a compressed spring will be slightly more massive than before it was compressed. Likewise, whenever energy is transferred between systems by any mechanism, an associated mass is transferred with it.
Any form of energy may be transformed into another form. For example, all types of potential energy are converted into kinetic energy when the objects are given freedom to move to different position (as for example, when an object falls off a support). When energy is in a form other than thermal energy, it may be transformed with good or even perfect efficiency, to any other type of energy, including electricity or production of new particles of matter. With thermal energy, however, there are often limits to the efficiency of the conversion to other forms of energy, as described by the second law of thermodynamics.
In all such energy transformation processes, the total energy remains the same, and a transfer of energy from one system to another, results in a loss to compensate for any gain. This principle, the conservation of energy, was first postulated in the early 19th century, and applies to any isolated system. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.[4]
Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy (and higher total energy) relative to the Earth.

Chemical law

Chemical law

Chemical laws are those laws of nature relevant to chemistry. The most fundamental concept in chemistry is the law of conservation of mass, which states that there is no detectable change in the quantity of matter during an ordinary chemical reaction. Modern physics shows that it is actually energy that is conserved, and that energy and mass are related; a concept which becomes important in nuclear chemistry. Conservation of energy leads to the important concepts of equilibrium, thermodynamics, and kinetics.
Additional laws of chemistry elaborate on the law of conservation of mass. Joseph Proust's law of definite composition says that pure chemicals are composed of elements in a definite formulation; we now know that the structural arrangement of these elements is also important.
Dalton's law of multiple proportions says that these chemicals will present themselves in proportions that are small whole numbers (i.e. 1:2 O:H in water); although in many systems (notably biomacromolecules and minerals) the ratios tend to require large numbers, and are frequently represented as a fraction. Such compounds are known as non-stoichiometric compounds
More modern laws of chemistry define the relationship between energy and transformations.
In equilibrium, molecules exist in mixture defined by the transformations possible on the timescale of the equilibrium, and are in a ratio defined by the intrinsic energy of the molecules—the lower the intrinsic energy, the more abundant the molecule.
Transforming one structure to another requires the input of energy to cross an energy barrier; this can come from the intrinsic energy of the molecules themselves, or from an external source which will generally accelerate transformations. The higher the energy barrier, the slower the transformation occurs.
There is a hypothetical intermediate, or transition structure, that corresponds to the structure at the top of the energy barrier. The Hammond-Leffler Postulate states that this structure looks most similar to the product or starting material which has intrinsic energy closest to that of the energy barrier. Stabilizing this hypothetical intermediate through chemical interaction is one way to achieve catalysis.
All chemical processes are reversible (law of microscopic reversibility) although some processes have such an energy bias, they are essentially irreversible.

Chemical reaction

A thermite reaction using iron(III) oxide. The sparks flying outwards are globules of molten iron trailing smoke in their wake.



Video demonstrating a chemical reaction.
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.[1] Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles (such as illustrated by Feynman diagrams), as well as nuclear reactions.
The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction mechanism. Chemical reactions are described with chemical equations, which graphically present the starting materials, end products, and sometimes intermediate products and reaction conditions.
Different chemical reactions are used in combination in chemical synthesis in order to obtain a desired product. In biochemistry, series of chemical reactions catalyzed by enzymes form metabolic pathways, by which syntheses and decompositions impossible under ordinary conditions are performed within a cell.

History

Chemical reactions such as combustion in the fire, fermentation and the reduction of ores to metals were known since antiquity. Initial theories of transformation of materials were developed by Greek philosophers, such as the Four-Element Theory of Empedocles stating that any substance is composed of the four basic elements – fire, water, air and earth. In the Middle Ages, chemical transformations were studied by Alchemists. They attempted, in particular, to convert lead into gold, for which purpose they used reactions of lead and lead-copper alloys with sulfur.[2]
The production of chemical substances that do not normally occur in nature has long been tried, such as the synthesis of sulfuric and nitric acids attributed to the controversial alchemist Jābir ibn Hayyān. The process involved heating of sulfate and nitrate minerals such as copper sulfate, alum and saltpeter. In the 17th century, Johann Rudolph Glauber produced hydrochloric acid and sodium sulfate by reacting sulfuric acid and sodium chloride. With the development of the lead chamber process in 1746 and the Leblanc process, allowing large-scale production of sulfuric acid and sodium carbonate, respectively, chemical reactions became implemented into the industry. Further optimization of sulfuric acid technology resulted in the contact process in 1880s,[3] and the Haber process was developed in 1909–1910 for ammonia synthesis.[4]
From the 16th century, researchers including Jan Baptist van Helmont, Robert Boyle and Isaac Newton tried to establish theories of the experimentally observed chemical transformations. The phlogiston theory was proposed in 1667 by Johann Joachim Becher. It postulated the existence of a fire-like element called "phlogiston", which was contained within combustible bodies and released during combustion. This proved to be false in 1785 by Antoine Lavoisier who found the correct explanation of the combustion as reaction with oxygen from the air.[5]
Joseph Louis Gay-Lussac recognized in 1808 that gases always react in a certain relationship with each other. Based on this idea and the atomic theory of John Dalton, Joseph Proust had developed the law of definite proportions, which later resulted in the concepts of stoichiometry and chemical equations.[6]
Regarding the organic chemistry, it was long believed that compounds obtained from living organisms were too complex to be obtained synthetically. According to the concept of vitalism, organic matter was endowed with a "vital force" and distinguished from inorganic materials. This separation was ended however by the synthesis of urea from inorganic precursors by Friedrich Wöhler in 1828. Other chemists who brought major contributions to organic chemistry include Alexander William Williamson with his synthesis of ethers and Christopher Kelk Ingold, who, among many discoveries, established the mechanisms of substitution reactions.a

Chemical substance

In chemistry, a chemical substance is a form of matter that has constant chemical composition and characteristic properties.[1] It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. They can be solids, liquids or gases.

Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, table salt (sodium chloride) and refined sugar (sucrose). However, simple or seemingly pure substances found in nature can in fact be mixtures of chemical substances. For example, tap water may contain small amounts of dissolved sodium chloride and compounds containing iron, calcium and many other chemical substances.

Chemical substances exist as solids, liquids, gases, or plasma and may change between these phases of matter with changes in temperature or pressure. Chemical reactions convert one chemical substance into another.

Forms of energy, such as light and heat, are not considered to be matter, and thus they are not "substances" in this regard.

Definition

Colors of a single chemical (Nile red) in different solvents, under visible and UV light.
Chemical substances (also called pure substances) are often defined as "any material with a definite chemical composition" in most introductory general chemistry textbooks.[2] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[3] The chemical substance index published by CAS also includes several alloys of uncertain composition.[4] Non-stoichiometric compounds are a special case (in inorganic chemistry) that violates the law of constant composition, and for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature"[5]
In geology, substances of uniform composition are called minerals, while physical mixtures (aggregates) of several minerals (different substances) are defined as rocks. Many minerals, however, mutually dissolve into solid solutions, such that a single rock is a uniform substance despite being a 'mixture'. Feldspars are a common example: anorthoclase is an alkali aluminum silicate, where the alkali metal is interchangeably either sodium or potassium.


History

The concept of a "chemical substance" became firmly established in the late eighteenth century after work by the chemist Joseph Proust on the composition of some pure chemical compounds such as basic copper carbonate.[6] He deduced that, "All samples of a compound have the same composition; that is, all samples have the same proportions, by mass, of the elements present in the compound." This is now known as the law of constant composition.[7] Later with the advancement of methods for chemical synthesis particularly in the realm of organic chemistry; the discovery of many more chemical elements and new techniques in the realm of analytical chemistry used for isolation and purification of elements and compounds from chemicals that led to the establishment of modern chemistry, the concept was defined as is found in most chemistry textbooks. However, there are some controversies regarding this definition mainly because the large number of chemical substances reported in chemistry literature need to be indexed.


Chemical elements

Native sulfur crystals. Sulfur occurs naturally as elemental sulfur, in sulfide and sulfate minerals and in hydrogen sulfide.
Main article: Chemical element
See also: List of elements by name
An element is a chemical substance that is made up of a particular kind of atoms and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmutated into another element through a nuclear reaction. This is so, because all of the atoms in a sample of an element have the same number of protons, though they may be different isotopes, with differing numbers of neutrons.
There are about 120 known elements, about 80 of which are stable – that is, they do not change by radioactive decay into other elements. However, the number of chemical substances that are elements can be more than 120, because some elements can occur as more than a single chemical substance (allotropes). For instance, oxygen exists as both diatomic oxygen (O2) and ozone (O3). The majority of elements are classified as metals. These are elements with a characteristic lustre such as iron, copper, and gold. Metals typically conduct electricity and heat well, and they are malleable and ductile.[8] Around a dozen elements,[9] such as carbon, nitrogen, and oxygen, are classified as non-metals. Non-metals lack the metallic properties described above, they also have a high electronegativity and a tendency to form negative ions. Certain elements such as silicon sometimes resemble metals and sometimes


Chemical compounds

Main article: Chemical compound
See also: List of organic compounds and List of inorganic compounds
A pure chemical compound is a chemical substance that is composed of a particular set of molecules or ions. Two or more elements combined into one substance through a chemical reaction form a chemical compound. All compounds are substances, but not all substances are compounds.
A chemical compound can be either atoms bonded together in molecules or crystals in which atoms, molecules or ions form a crystalline lattice. Compounds based primarily on carbon and hydrogen atoms are called organic compounds, and all others are called inorganic compounds. Compounds containing bonds between carbon and a metal are called organometallic compounds.
Compounds in which components share electrons are known as covalent compounds. Compounds consisting of oppositely charged ions are known as ionic compounds, or salts.
In organic chemistry, there can be more than one chemical compound with the same composition and molecular weight. Generally, these are called isomers. Isomers usually have substantially different chemical properties, may be isolated and do not spontaneously convert to each other. A common example is glucose vs. fructose. The former is an aldehyde, the latter is a ketone. Their interconversion requires either enzymatic or acid-base catalysis. However, there are also tautomers, where isomerization occurs spontaneously, such that a pure substance cannot be isolated into its tautomers. A common example is glucose, which has open-chain and ring forms. One cannot manufacture pure open-chain glucose because glucose spontaneously cyclizes to the hemiacetal form.

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements[1][2][3] that can be separated into simpler substances by chemical reactions.[4] Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms[3] that are held together in a defined spatial arrangement by chemical bonds. Chemical compounds can be molecular compounds held together by covalent bonds, salts held together by ionic bonds, intermetallic compounds held together by metallic bonds, or complexes held together by coordinate covalent bonds. Pure chemical elements are not considered chemical compounds, even if they consist of molecules which contain only multiple atoms of a single element (such as H2, S8, etc.),[5] which are called diatomic molecules or polyatomic molecules.

Wider definitions

There are exceptions to the definition above, and large amounts of the solid chemical matter familiar on Earth do not have simple formulas. Certain crystalline compounds are called "non-stoichiometric" because they vary in composition due to either the presence of foreign elements trapped within the crystal structure or a deficit or excess of the constituent elements. Such non-stoichiometric chemical compounds form most of the crust and mantle of the Earth.

Other compounds regarded as chemically identical may have varying amounts of heavy or light isotopes of the constituent elements, which will make the ratio of elements by mass vary slightly.

Elementary concepts

Characteristic properties of compounds:

Elements in a compound are present in a definite proportion

Example- 2 atoms of hydrogen + 1 atom of oxygen becomes 1 molecule of compound-water.

Compounds have a definite set of properties

Elements comprising a compound do not retain their original properties.

Example: hydrogen (element, which is combustible and non-supporter of combustion) + oxygen (element, which is non-combustible and supporter of combustion) becomes water (compound, which is non-combustible and non-supporter of combustion)

Valency is the number of hydrogen atoms which can combine with one atom of the element forming a compound.

Compounds compared to mixtures

The physical and chemical properties of compounds are different from those of their constituent elements. This is one of the main criteria for distinguishing a compound from a mixture of elements or other substances because a mixture's properties are generally closely related to and dependent on the properties of its constituents. Another criterion for distinguishing a compound from a mixture is that the constituents of a mixture can usually be separated by simple, mechanical means such as filtering, evaporation, or use of a magnetic force, but the components of a compound can only be separated by a chemical reaction. Conversely, mixtures can be created by mechanical means alone, but a compound can only be created (either from elements or from other compounds, or a combination of the two) by a chemical reaction.

Some mixtures are so intimately combined that they have some properties similar to compounds and may easily be mistaken for compounds. One example is alloys. Alloys are made mechanically, most commonly by heating the constituent metals to a liquid state, mixing them thoroughly, and then cooling the mixture quickly so that the constituents are trapped in the base metal. Other examples of compound-like mixtures include intermetallic compounds and solutions of alkali metals in a liquid form of ammonia.

Chemical element

A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminium, iron, copper, gold, mercury, and lead.

As of November 2011, 118 elements have been identified, the latest being ununseptium in 2010.[1] Of the 118 known elements, only the first 98 are known to occur naturally on Earth. Of these, 80 are stable, while the others are radioactive, decaying into lighter elements over various timescales from fractions of a second to billions of years. Those elements that do not occur naturally on Earth have been produced artificially as the synthetic products of man-made nuclear reactions.

Hydrogen and helium are by far the most abundant elements in the universe. However, iron is the most abundant element (by mass) making up the Earth, and oxygen is the most common element in the Earth's crust.[2] Although all known chemical matter is composed of these elements, chemical matter itself constitutes only about 15% of the matter in the universe. The remainder is dark matter, a mysterious substance which is not composed of chemical elements since it lacks protons, neutrons or electrons.[3]

The chemical elements are thought to have been produced by various cosmic processes, including hydrogen, helium (and smaller amounts of lithium, beryllium and boron) created during the Big Bang and cosmic-ray spallation. Production of heavier elements, from carbon to the very heaviest elements, proceeds by stellar nucleosynthesis, and these were made available for later solar system and planetary formation by supernovae, which blast these elements into space.[4] The high abundance of oxygen, silicon, and iron on Earth reflect their common production in such stars, after the lighter gaseous elements and their compounds have been subtracted. While most elements are generally viewed as stable, a small amount of natural transformation of one element to another also occurs in the present time, through decay of radioactive elements as well as other natural nuclear processes.

Relatively pure samples of isolated elements are uncommon in nature. While all of the 98 naturally occurring elements have been identified in mineral samples from the Earth's crust, only a small minority of elements are found as recognizable, relative pure minerals. Among the more common of such "native elements" are copper, silver, gold, carbon (as coal, graphite, or diamonds), sulfur, and mercury. All but a few of the most inert elements, such as noble gases and noble metals, are usually found on Earth in chemically combined form, as chemical compounds. While about 32 of the chemical elements occur on Earth in native uncombined form, most of these occur as mixtures. For example, atmospheric air is primarily a mixture of nitrogen, oxygen, and argon, and native solid elements occur in alloys, such as that of iron and nickel.

When two distinct elements are chemically combined, with the atoms held together by chemical bonds, the result is termed a chemical compound. Two thirds of the chemical elements occur on Earth only as compounds, and in the remaining third, often the compound forms of the element are most common.[citation needed] Chemical compounds may be composed of elements combined in exact whole-number ratios of atoms, as in water, table salt, and minerals as quartz, calcite, and some ores. However, chemical bonding of many types of elements results in crystalline solids and metallic alloys for which exact chemical formulas do not exist.

The history of discovery and use of the elements began with primitive human societies that found native elements like copper and gold, and extracted (smelted) iron and a few other metals from their ores. Alchemists and chemists subsequently identified many more, with nearly all of the naturally-occurring elements known by 1900. The properties of the chemical elements are often summarized using the periodic table that organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties. Either in its pure forms, or in various chemical compounds or mixtures, almost every element has at least one important human use. Save for short half-lived radioactive elements, all of the elements are available industrially, most to high degrees of purity.

Around two dozen of the elements are essential to various kinds of biological life. Most rare elements on Earth are not needed by life (exceptions being selenium and iodine), while a few quite common ones (aluminium and titanium) are not used. Most organisms share element needs, with a few differences. For example, ocean algae use bromine but land plants and animals seem to need none, and all animals require sodium, but some plants do not. Just six elements—carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus—make up almost 99% of the mass of a human body (see composition of the human body for a complete list). In addition to the six major elements that compose most of the human body, humans require consumption of at least a dozen more elements in the form of certain chemical compounds.

Atom

The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutrons). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive charge if there are fewer electrons (electron deficiency) or negative charge if there are more electrons (electron excess). A positively or negatively charged atom is known as an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determines the isotope of the element.[1]

The name atom comes from the Greek ἄτομος (atomos, "indivisible") from ἀ- (a-, "not") and τέμνω (temnō, "I cut"),[2] which means uncuttable, or indivisible, something that cannot be divided further.[3] The concept of an atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers. In the 17th and 18th centuries, chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. During the late 19th and early 20th centuries, physicists discovered subatomic components and structure inside the atom, thereby demonstrating that the 'atom' was divisible. The principles of quantum mechanics were used to successfully model the atom.[4][5]

Atoms are minuscule objects with proportionately tiny masses. Atoms can only be observed individually using special instruments such as the scanning tunneling microscope. Over 99.94% of an atom's mass is concentrated in the nucleus,[note 1] with protons and neutrons having roughly equal mass. Each element has at least one isotope with unstable nuclei that can undergo radioactive decay. This can result in a transmutation that changes the number of protons or neutrons in a nucleus.[6] Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emitting photons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties.

Etymology

he word chemistry comes from the word alchemy, an earlier set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism and medicine; it is commonly thought of as the quest to turn lead or another common starting material into gold.[26] The word alchemy in turn is derived from the Arabic word al-kīmīā (الكيمياء), meaning alchemy. The Arabic term is borrowed from the Greek χημία or χημεία.[27][28] This may have Egyptian origins. Many believe that al-kīmīā is derived from χημία, which is in turn derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian.[27] Alternately, al-kīmīā may be derived from χημεία, meaning "cast together".[29]

An alchemist was called a 'chemist' in popular speech, and later the suffix "-ry" was added to this to describe the art of the chemist as "chemistry".

Definitions

In retrospect, the definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. Shown below are some of the standard definitions used by various noted chemists:

Alchemy (330) – the study of the composition of waters, movement, growth, embodying, disembodying, drawing the spirits from bodies and bonding the spirits within bodies (Zosimos).[30]

Chymistry (1661) – the subject of the material principles of mixed bodies (Boyle).[31]

Chymistry (1663) – a scientific art, by which one learns to dissolve bodies, and draw from them the different substances on their composition, and how to unite them again, and exalt them to a higher perfection (Glaser).[32]

Chemistry (1730) – the art of resolving mixed, compound, or aggregate bodies into their principles; and of composing such bodies from those principles (Stahl).[33]

Chemistry (1837) – the science concerned with the laws and effects of molecular forces (Dumas).[34]

Chemistry (1947) – the science of substances: their structure, their properties, and the reactions that change them into other substances (Pauling).[35]

Chemistry (1998) – the study of matter and the changes it undergoes (Chang).[36]

Uranium

Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. The uranium nucleus binds between 141 and 146 neutrons, establishing six isotopes (U-233 through U-238), the most common of which are uranium-238 (146 neutrons) and uranium-235 (143 neutrons). All isotopes are unstable and uranium is weakly radioactive. Uranium has the second highest atomic weight of the naturally occurring elements, lighter only than plutonium-244.[3] Its density is about 70% higher than that of lead, but not as dense as gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.

In nature, uranium is found as uranium-238 (99.2739–99.2752%), uranium-235 (0.7198–0.7202%), and a very small amount of uranium-234 (0.0050–0.0059%).[4] Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years,[5] making them useful in dating the age of the Earth.

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 has the distinction of being the only naturally occurring fissile isotope. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology. While uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons, uranium-235 and to a lesser degree uranium-233 have a much higher fission cross-section for slow neutrons. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors, and produces the fissile material for nuclear weapons. Depleted uranium (238U) is used in kinetic energy penetrators and armor plating.[6]

Uranium is used as a colorant in uranium glass, producing orange-red to lemon yellow hues. It was also used for tinting and shading in early photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal and its radioactive properties were discovered in 1896 by Antoine Becquerel. Research by Enrico Fermi and others starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239. The security of those weapons and their fissile material following the breakup of the Soviet Union in 1991 is an ongoing concern for public health and safety.[7] See Nuclear proliferation.

Chemical element

A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminium, iron, copper, gold, mercury, and lead.

As of November 2011, 118 elements have been identified, the latest being ununseptium in 2010.[1] Of the 118 known elements, only the first 98 are known to occur naturally on Earth. Of these, 80 are stable, while the others are radioactive, decaying into lighter elements over various timescales from fractions of a second to billions of years. Those elements that do not occur naturally on Earth have been produced artificially as the synthetic products of man-made nuclear reactions.

Hydrogen and helium are by far the most abundant elements in the universe. However, iron is the most abundant element (by mass) making up the Earth, and oxygen is the most common element in the Earth's crust.[2] Although all known chemical matter is composed of these elements, chemical matter itself constitutes only about 15% of the matter in the universe. The remainder is dark matter, a mysterious substance which is not composed of chemical elements since it lacks protons, neutrons or electrons.[3]

The chemical elements are thought to have been produced by various cosmic processes, including hydrogen, helium (and smaller amounts of lithium, beryllium and boron) created during the Big Bang and cosmic-ray spallation. Production of heavier elements, from carbon to the very heaviest elements, proceeds by stellar nucleosynthesis, and these were made available for later solar system and planetary formation by supernovae, which blast these elements into space.[4] The high abundance of oxygen, silicon, and iron on Earth reflect their common production in such stars, after the lighter gaseous elements and their compounds have been subtracted. While most elements are generally viewed as stable, a small amount of natural transformation of one element to another also occurs in the present time, through decay of radioactive elements as well as other natural nuclear processes.

Relatively pure samples of isolated elements are uncommon in nature. While all of the 98 naturally occurring elements have been identified in mineral samples from the Earth's crust, only a small minority of elements are found as recognizable, relative pure minerals. Among the more common of such "native elements" are copper, silver, gold, carbon (as coal, graphite, or diamonds), sulfur, and mercury. All but a few of the most inert elements, such as noble gases and noble metals, are usually found on Earth in chemically combined form, as chemical compounds. While about 32 of the chemical elements occur on Earth in native uncombined form, most of these occur as mixtures. For example, atmospheric air is primarily a mixture of nitrogen, oxygen, and argon, and native solid elements occur in alloys, such as that of iron and nickel.

When two distinct elements are chemically combined, with the atoms held together by chemical bonds, the result is termed a chemical compound. Two thirds of the chemical elements occur on Earth only as compounds, and in the remaining third, often the compound forms of the element are most common.[citation needed] Chemical compounds may be composed of elements combined in exact whole-number ratios of atoms, as in water, table salt, and minerals as quartz, calcite, and some ores. However, chemical bonding of many types of elements results in crystalline solids and metallic alloys for which exact chemical formulas do not exist.

The history of discovery and use of the elements began with primitive human societies that found native elements like copper and gold, and extracted (smelted) iron and a few other metals from their ores. Alchemists and chemists subsequently identified many more, with nearly all of the naturally-occurring elements known by 1900. The properties of the chemical elements are often summarized using the periodic table that organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties. Either in its pure forms, or in various chemical compounds or mixtures, almost every element has at least one important human use. Save for short half-lived radioactive elements, all of the elements are available industrially, most to high degrees of purity.

Around two dozen of the elements are essential to various kinds of biological life. Most rare elements on Earth are not needed by life (exceptions being selenium and iodine), while a few quite common ones (aluminium and titanium) are not used. Most organisms share element needs, with a few differences. For example, ocean algae use bromine but land plants and animals seem to need none, and all animals require sodium, but some plants do not. Just six elements—carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus—make up almost 99% of the mass of a human body (see composition of the human body for a complete list). In addition to the six major elements that compose most of the human body, humans require consumption of at least a dozen more elements in the form of certain chemical compounds.

Periodic table

The periodic table is a tabular display of the chemical elements, organized on the basis of their properties. Elements are presented in increasing atomic number. While rectangular in general outline, gaps are included in the rows or periods to keep elements with similar properties together, such as the halogens and the noble gases, in columns or groups, forming distinct rectangular areas orblocks. Because the periodic table accurately predicts the properties of various elements and the relations between properties, its use is widespread within chemistry, providing a useful framework for analysing chemical behavior, as well as in other sciences.

Although precursors exist, the current table is generally credited to Dmitri Mendeleev, who developed it in 1869 to illustrate periodic trends in the properties of the then-known elements; the layout has been refined and extended as new elements have been discovered and new theoretical models developed to explain chemical behavior. Mendeleev's presentation also predicted some properties of then-unknown elements expected to fill gaps in his arrangement; these predictions were proved correct when those elements were discovered and found to have properties close to the predictions.

All elements from atomic numbers 1 (hydrogen) to 118 (ununoctium) have been isolated. Of these, all up to californium exist naturally; the rest have only been artificially synthesised in laboratories, along with numerous synthetic radionuclides of naturally occurring elements. Production of elements beyond ununoctium is being pursued, with the question of how the periodic table may need to be modified to accommodate these elements being a matter of ongoing debate.

History

Main article: History of the periodic table

Dmitri Mendeleev

Previous attempts at systemization

In 1789, Antoine Lavoisier published a list of 33 chemical elements. Although Lavoisier grouped the elements into gases, metals, nonmetals, and earths,[1] chemists spent the following century searching for a more precise classification scheme. In 1829, Johann Wolfgang Döbereiner observed that many of the elements could be grouped into triads (groups of three) based on their chemical properties. Lithium, sodium, and potassium, for example, were grouped together as soft, reactive metals. Döbereiner also observed that, when arranged by atomic weight, the second member of each triad was roughly the average of the first and the third.[2] This became known as the Law of Triads.[3] German chemist Leopold Gmelin worked with this system, and by 1843 he had identified ten triads, three groups of four, and one group of five. Jean-Baptiste Dumas published work in 1857 describing relationships between various groups of metals. Although various chemists were able to identify relationships between small groups of elements, they had yet to build one scheme that encompassed them all.[2]

German chemist August Kekulé had observed in 1858 that carbon has a tendency to bond with other elements in a ratio of one to four. Methane, for example, has one carbon atom and four hydrogen atoms. This concept eventually became known as valency. In 1864, fellow German chemist Julius Lothar Meyer published a table of the 49 known elements arranged by valency. The table revealed that elements with similar properties often shared the same valency.[4]

English chemist John Newlands produced a series of papers in 1864 and 1865 that described his own classification of the elements: He noted that when listed in order of increasing atomic weight, similar physical and chemical properties recurred at intervals of eight, which he likened to the octaves of music.[5][6] This Law of Octaves, however, was ridiculed by his contemporaries, and the Chemical Society refused to publish his work.[7] Nonetheless, Newlands was able to draft an atomic table and use it to predict the existence of missing elements, such as germanium. The Chemical Society only acknowledged the significance of his discoveries some five years after they credited Mendeleev.[citation needed]

Mendeleev's table

Mendeleev's 1869 periodic table; note that his arrangement presents the periods vertically, and the groups horizontally

Russian chemistry professor Dmitri Ivanovich Mendeleev and German chemist Julius Lothar Meyer independently published their periodic tables in 1869 and 1870, respectively.[8] They both constructed their tables in a similar manner: By listing the elements in a row or column in order of atomic weight and starting a new row or column when the characteristics of the elements began to repeat.[9] The success of Mendeleev's table came from two decisions he made: The first was to leave gaps in the table when it seemed that the corresponding element had not yet been discovered.[10] Mendeleev was not the first chemist to do so, but he was the first to be recognized as using the trends in his periodic table to predict the properties of those missing elements, such as gallium and germanium.[11] The second decision was to occasionally ignore the order suggested by the atomic weights and switch adjacent elements, such as cobalt and nickel, to better classify them into chemical families. With the development of theories of atomic structure, it became apparent that Mendeleev had listed the elements in order of increasing atomic number.[12]

Further development

In the years following publication of Mendeleev's periodic table, the gaps he identified were filled as chemists discovered additional naturally occurring elements.[13] It is often stated that the last naturally occurring element to be discovered was francium (referred to by Mendeleev as eka-caesium) in 1939.[14] However, plutonium, produced synthetically in 1940, was identified in trace quantities as a naturally occurring primordial element in 1971.[15]

With the development of modern quantum mechanical theories of electron configurations within atoms, it became apparent that each row (or period) in the table corresponded to the filling of a quantum shell of electrons. In Mendeleev's original table, each period was the same length. However, because larger atoms have more electron sub-shells, modern tables have progressively longer periods further down the table.[16]

The production of various transuranic elements has expanded the periodic table significantly, the first of these being neptunium, synthesized in 1939.[17] Because many of the transuranic elements are highly unstable and decay quickly, they are challenging to detect and characterize when produced, and there have been controversies concerning the acceptance of competing discovery claims for some elements, requiring independent review to determine which party has priority, and hence naming rights. The most recently named element is copernicium (number 112), named on 19 February 2010;[18] the most recently accepted discoveries are ununquadium (114) and ununhexium (116), both accepted on 1 June 2011.[19]. In 2010, a joint Russia–US collaboration at Dubna, Moscow Oblast, Russia, claimed to have synthesized six atoms of ununseptium, making it the most recently claimed discovery.

Jābir ibn Hayyān

Abu Mūsā Jābir ibn Hayyān (al-Azdi / al-Kufi / al-Tusi / al-Sufi), often known simply as Geber, (Persian/Arabic: جابر بن حیان) (born c. 721 in Tus, Persia; died c. 815 in Kufa, Iraq)[6] was a prominent polymath: a chemist and alchemist, astronomer and astrologer, engineer, geographer, philosopher, physicist, and pharmacist and physician. Born and educated in Tus, he later traveled to Kufa. Jābir is held to have been the first practical alchemist.[7]
As early as the tenth century, the identity and exact corpus of works of Jābir was in dispute in Islamic circles.[8] His name was Latinized as "Geber" in the Christian West and in 13th century Europe an anonymous writer, usually referred to as Pseudo-Geber, produced alchemical and metallurgical writings under the pen-name Geber.

Biography

Early references

In 987 Ibn al-Nadim compiled the Kitab al-Fihrist which mentions Jabir as a spiritual leader and as a companion to Jafar as-Sadiq (he is not listed among the students of Jafar as-Sadiq but many of the writings of the Jabirian corpus are dedicated to Jafar as-Sadiq). In another reference al-Nadim reports that a group philosophers claimed Jabir was one of their own members. Another group, reported by al-Nadim, says only The Large Book of Mercy is genuine and that the rest are pseudographical. Their assertions are rejected by al-Nadim.[9] Joining al-Nadim in asserting a real Jabir; Ibn-Wahshiyya ("Jaber ibn Hayyn al-Sufi ...book on poison is a great work..") Rejecting a real Jabir; (the philosopher c.970) Abu Sulayman al-Mantiqi claims the real author is one al-Hasan ibn al-Nakad al-Mawili. 14th century critic of Arabic literature, Jamal al-Din ibn Nubata al-Misri declares all the writings attributed to Jabir doubtful.[10]

Life and background

Jabir was a Natural Philosopher who lived mostly in the 8th century, he was born in Tus, Khorasan, in Iran (Persia),[6] then ruled by the Umayyad Caliphate. Jabir in the classical sources has the been entitled differently as al-Azdi or al-Kufi or al-Tusi or al-Sufi.[11] There is a difference of opinion[11] as to whether he was an Arab from Kufa who lived in Khurasan or a Persian from Khorasan who later went to Kufa or whether he was, as some have suggested, of Syrian origin and later lived in Persia and Iraq.[11] His ethnic background is not clear,[11] and sources reference him as an Arab or a Persian.[1] In some sources, he is reported to have been the son of Hayyan al-Azdi, a pharmacist of the Arabian Azd tribe who emigrated from Yemen to Kufa (in present-day Iraq) during the Umayyad Caliphate.[12][13] while Henry Corbin believes Geber seems to have been a client of the 'Azd tribe.[14] Jābir became an alchemist at the court of Caliph Harun al-Rashid, for whom he wrote the Kitab al-Zuhra ("The Book of Venus", on "the noble art of alchemy").[citation needed] Hayyan had supported the Abbasid revolt against the Umayyads, and was sent by them to the province of Khorasan (present day Afghanistan and Iran) to gather support for their cause. He was eventually caught by the Ummayads and executed. His family fled to Yemen,[12][15] where Jābir grew up and studied the Quran, mathematics and other subjects.[12] Jābir's father's profession may have contributed greatly to his interest in alchemy.

After the Abbasids took power, Jābir went back to Kufa. He began his career practicing medicine, under the patronage of a Vizir (from the noble Persian family Barmakids) of Caliph Harun al-Rashid. His connections to the Barmakid cost him dearly in the end. When that family fell from grace in 803, Jābir was placed under house arrest in Kufa, where he remained until his death.

It has been asserted that Jābir was a student of the sixth Imam Ja'far al-Sadiq and Harbi al-Himyari,[5][8] however other scholars have questioned this theory.[16]

The Jabirian corpus

An illustration of the various experiments and instruments used by Jabir Ibn Hayyan.

In total, nearly 3,000 treatises and articles are credited to Jabir ibn Hayyan.[17] Following the pioneering work of Paul Kraus, who demonstrated that a corpus of some several hundred works ascribed to Jābir were probably a medley from different hands,[10][18] mostly dating to the late ninth and early tenth centuries, many scholars believe that many of these works consist of commentaries and additions by his followers,[citation needed] particularly of an Ismaili persuasion.[19]

The scope of the corpus is vast: cosmology, music, medicine, magic, biology, chemical technology, geometry, grammar, metaphysics, logic, artificial generation of living beings, along with astrological predictions, and symbolic Imâmî myths.[10]

The 112 Books dedicated to the Barmakids, viziers of Caliph Harun al-Rashid. This group includes the Arabic version of the Emerald Tablet, an ancient work that proved a recurring foundation of and source for alchemical operations. In the Middle Ages it was translated into Latin (Tabula Smaragdina) and widely diffused among European alchemists.

The Seventy Books, most of which were translated into Latin during the Middle Ages. This group includes the Kitab al-Zuhra ("Book of Venus") and the Kitab Al-Ahjar ("Book of Stones").

The Ten Books on Rectification, containing descriptions of alchemists such as Pythagoras, Socrates, Plato and Aristotle.

The Books on Balance; this group includes his most famous 'Theory of the balance in Nature'.

Jābir states in his Book of Stones (4:12) that "The purpose is to baffle and lead into error everyone except those whom God loves and provides for". His works seem to have been deliberately written in highly esoteric code (see steganography), so that only those who had been initiated into his alchemical school could understand them. It is therefore difficult at best for the modern reader to discern which aspects of Jābir's work are to be read as symbols (and what those symbols mean), and what is to be taken literally. Because his works rarely made overt sense, the term gibberish is believed to have originally referred to his writings (Hauck, p. 19).

People

Jābir's interest in alchemy was probably inspired by his teacher Ja'far as-Sadiq. When he used to talk about alchemy, he would say "my master Ja'far as-Sadiq taught me about calcium, evaporation, distillation and crystallization and everything I learned in alchemy was from my master Ja'far as-Sadiq." However, it has been proved that there is no connection between Jābir and Ja'far as-Sadiq [20] . It seems the claimed connection is based on traditional religious historians. Ibn Hayyan was deeply religious, and repeatedly emphasizes in his works that alchemy is possible only by subjugating oneself completely to the will of Allah and becoming a literal instrument of Allah on Earth, since the manipulation of reality is possible only for Allah. The Book of Stones prescribes long and elaborate sequences of specific prayers that must be performed without error alone in the desert before one can even consider alchemical experimentation.

Jābir professes to draw his inspiration from earlier writers, legendary and historic, on the subject.[21] In his writings, Jābir pays tribute to Egyptian and Greek alchemists Zosimos, Democritus, Hermes Trismegistus, Agathodaimon, but also Plato, Aristotle, Galen, Pythagoras, and Socrates as well as the commentators Alexander of Aphrodisias Simplicius, Porphyry and others.[10] A huge pseudo-epigraphic literature of alchemical books was composed in Arabic, among which the names of Persian authors also appear like Jāmāsb, Ostanes, Mani, testifying that alchemy-like operations on metals and other substances were also practiced in Persia. The great number of Persian technical names (zaybaq = mercury, nošāder = sal-ammoniac) also corroborates the idea of an important Iranian root of medieval alchemy.[22] Ibn al-Nadim reports a dialogue between Aristotle and Ostanes, the Persian alchemist of Achaemenid era, which is in Jabirian corpus under the title of Kitab Musahhaha Aristutalis.[23] Ruska had suggested that the Sasanian medical schools played an important role in the spread of interest in alchemy.[22] He emphasizes the long history of alchemy, "whose origin is Arius ... the first man who applied the first experiment on the [philosopher's] stone... and he declares that man possesses the ability to imitate the workings of Nature" (Nasr, Seyyed Hussein, Science and Civilization of Islam).

Theories

Jābir's alchemical investigations ostensibly revolved around the ultimate goal of takwin — the artificial creation of life. The Book of Stones includes several recipes for creating creatures such as scorpions, snakes, and even humans in a laboratory environment, which are subject to the control of their creator. What Jābir meant by these recipes is unknown.

Jābir's alchemical investigations were theoretically grounded in an elaborate numerology related to Pythagorean and Neoplatonic systems. The nature and properties of elements was defined through numeric values assigned the Arabic consonants present in their name, ultimately culminating in the number 17.

By Jabirs' time Aristotelian physics, had become Neoplatonic. Each Aristotelian element was composed of these qualities: fire was both hot and dry, earth, cold and dry, water cold and moist, and air, hot and moist. This came from the elementary qualities which are theoretical in nature plus substance. In metals two of these qualities were interior and two were exterior. For example, lead was cold and dry and gold was hot and moist. Thus, Jābir theorized, by rearranging the qualities of one metal, a different metal would result. Like Zosimos, Jabir believed this would require a catalyst, an al-iksir, the elusive elixir that would make this transformation possible — which in European alchemy became known as the philosopher's stone.[10]

According to Jabir's mercury-sulfur theory, metals differ from each in so far as they contain different proportions of the sulfur and mercury. These are not the elements that we know by those names, but certain principles to which those elements are the closest approximation in nature.[24] Based on Aristotle's "exhalation" theory the dry and moist exhalations become sulfur and mercury (sometimes called "sophic" or "philosophic" mercury and sulfur). The sulfur-mercury theory is first recorded in a 7th century work Secret of Creation credited (falsely) to Balinus (Apollonius of Tyana). This view becomes wide spread.[25] In the Book of Explanation Jabir says

the metals are all, in essence, composed of mercury combined and coagulated with sulphur [that has risen to it in earthy, smoke-like vapors]. They differ from one another only because of the difference of their accidental qualities, and this difference is due to the difference of their sulphur, which again is caused by a variation in the soils and in their positions with respect to the heat of the sun

Holmyard says that Jabir proves by experiment that these are not ordinary sulfur and mercury.[12]

The seeds of the modern classification of elements into metals and non-metals could be seen in his chemical nomenclature. He proposed three categories:[26]

"Spirits" which vaporise on heating, like arsenic (realgar, orpiment), camphor, mercury, sulfur, sal ammoniac, and ammonium chloride.

"Metals", like gold, silver, lead, tin, copper, iron, and khar-sini

Non-malleable substances, that can be converted into powders, such as stones.

The origins of the idea of chemical equivalents might be traced back to Jabir, in whose time it was recognized that "a certain quantity of acid is necessary in order to neutralize a given amount of base."[27][verification needed] Jābir also made important contributions to medicine, astronomy/astrology, and other sciences. Only a few of his books have been edited and published, and fewer still are available in translation.

Isaac Newton

Sir Isaac Newton PRS (25 December 1642 – 20 March 1727 [NS: 4 January 1643 – 31 March 1727])[1] was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."[7] His monograph Philosophiæ Naturalis Principia Mathematica, published in 1687, lays the foundations for most of classical mechanics. In this work, Newton described universal gravitation and the three laws of motion, which dominated the scientific view of the physical universe for the next three centuries. Newton showed that the motions of objects on Earth and of celestial bodies are governed by the same set of natural laws, by demonstrating the consistency between Kepler's laws of planetary motion and his theory of gravitation, thus removing the last doubts about heliocentrism and advancing the Scientific Revolution.

The Principia is generally considered to be one of the most important scientific books ever written, due, independently, to the specific physical laws the work successfully described, and for the style of the work, which assisted in setting standards for scientific publication down to the present time. Newton built the first practical reflecting telescope[8] and developed a theory of colour based on the observation that a prism decomposes white light into the many colours that form the visible spectrum. He also formulated an empirical law of cooling and studied the speed of sound. In mathematics, Newton shares the credit with Gottfried Leibniz for the development of differential and integral calculus. He also demonstrated the generalised binomial theorem, developed Newton's method for approximating the roots of a function, and contributed to the study of power series. Newton's work on infinite series was inspired by Simon Stevin's decimals.[9] Newton was also highly religious. He was an unorthodox Christian, and wrote more on Biblical hermeneutics and occult studies than on the subjects of science and mathematics. Newton secretly rejected Trinitarianism, fearing to be accused of refusing holy orders.

Early life

Main article: Early life of Isaac Newton

Isaac Newton was born on what is retroactively considered 4 January 1643 [OS: 25 December 1642][1] at Woolsthorpe Manor in Woolsthorpe-by-Colsterworth, a hamlet in the county of Lincolnshire. At the time of Newton's birth, England had not adopted the Gregorian calendar and therefore his date of birth was recorded as Christmas Day, 25 December 1642. Newton was born three months after the death of his father, a prosperous farmer also named Isaac Newton. Born prematurely, he was a small child; his mother Hannah Ayscough reportedly said that he could have fit inside a quart mug (≈ 1.1 litres). When Newton was three, his mother remarried and went to live with her new husband, the Reverend Barnabus Smith, leaving her son in the care of his maternal grandmother, Margery Ayscough. The young Isaac disliked his stepfather and held some enmity towards his mother for marrying him, as revealed by this entry in a list of sins committed up to the age of 19: "Threatening my father and mother Smith to burn them and the house over them."[11] While Newton was once engaged in his late teens to a Miss Storey, he never married, being highly engrossed in his studies and work.[12][13][14]

Newton in a 1702 portrait by Godfrey Kneller

Isaac Newton (Bolton, Sarah K. Famous Men of Science. NY: Thomas Y. Crowell & Co., 1889)

From the age of about twelve until he was seventeen, Newton was educated at The King's School, Grantham (where his alleged signature can still be seen upon a library window sill). He was removed from school, and by October 1659, he was to be found at Woolsthorpe-by-Colsterworth, where his mother, widowed by now for a second time, attempted to make a farmer of him. He hated farming.[15] Henry Stokes, master at the King's School, persuaded his mother to send him back to school so that he might complete his education. Motivated partly by a desire for revenge against a schoolyard bully, he became the top-ranked student.[16] The Cambridge psychologist Simon Baron-Cohen considers it "fairly certain" that Newton suffered from Asperger syndrome.[17]

In June 1661, he was admitted to Trinity College, Cambridge as a sizar – a sort of work-study role.[18] At that time, the college's teachings were based on those of Aristotle,[19] whom Newton supplemented with modern philosophers, such as Descartes, and astronomers such as Copernicus, Galileo, and Kepler. In 1665, he discovered the generalised binomial theorem and began to develop a mathematical theory that later became infinitesimal calculus. Soon after Newton had obtained his degree in August 1665, the university temporarily closed as a precaution against the Great Plague. Although he had been undistinguished as a Cambridge student,[20] Newton's private studies at his home in Woolsthorpe over the subsequent two years saw the development of his theories on calculus,[21] optics and the law of gravitation. In 1667, he returned to Cambridge as a fellow of Trinity.[22] Fellows were required to become ordained priests, something Newton desired to avoid due to his unorthodox views. Luckily for Newton, there was no specific deadline for ordination and it could be postponed indefinitely. The problem became more severe later when Newton was elected for the prestigious Lucasian Chair. For such a significant appointment, ordaining normally could not be dodged. Nevertheless, Newton managed to avoid it by means of a special permission from Charles II (see "Middle years" section below).

Middle years

Mathematics

Newton's work has been said "to distinctly advance every branch of mathematics then studied".[23] His work on the subject usually referred to as fluxions or calculus, seen in a manuscript of October 1666, is now published among Newton's mathematical papers,[24] the manuscript De analysi per aequationes numero terminorum infinitas sent by Isaac Barrow to John Collins in June 1669, Barrow identified to Collins in August of that year as:[25]

Mr Newton, a fellow of our College, and very young ... but of an extraordinary genius and proficiency in these things.

Newton later became involved in a dispute with Leibniz over priority in the development of infinitesimal calculus. Most modern historians believe that Newton and Leibniz developed infinitesimal calculus independently, although with very different notations. Occasionally it has been suggested that Newton published almost nothing about it until 1693, and did not give a full account until 1704, while Leibniz began publishing a full account of his methods in 1684. (Leibniz's notation and "differential Method", nowadays recognised as much more convenient notations, were adopted by continental European mathematicians, and after 1820 or so, also by British mathematicians.) Such a suggestion, however, fails to notice the content of calculus which critics of Newton's time and modern times have pointed out in Book 1 of Newton's Principia itself (published 1687) and in its forerunner manuscripts, such as De motu corporum in gyrum ("On the motion of bodies in orbit"), of 1684. The Principia is not written in the language of calculus either as we know it or as Newton's (later) 'dot' notation would write it. But his work extensively uses an infinitesimal calculus in geometric form, based on limiting values of the ratios of vanishing small quantities: in the Principia itself Newton gave demonstration of this under the name of 'the method of first and last ratios'[26] and explained why he put his expositions in this form,[27] remarking also that 'hereby the same thing is performed as by the method of indivisibles'.

Because of this, the Principia has been called "a book dense with the theory and application of the infinitesimal calculus" in modern times[28] and "lequel est presque tout de ce calcul" ('nearly all of it is of this calculus') in Newton's time.[29] His use of methods involving "one or more orders of the infinitesimally small" is present in his De motu corporum in gyrum of 1684[30] and in his papers on motion "during the two decades preceding 1684".[31]

Newton had been reluctant to publish his calculus because he feared controversy and criticism.[32] He had a very close relationship with Swiss mathematician Nicolas Fatio de Duillier, who from the beginning was impressed by Newton's gravitational theory. In 1691, Duillier planned to prepare a new version of Newton's Principia, but never finished it. However, in 1693 the relationship between the two men changed. At the time, Duillier had also exchanged several letters with Leibniz.[33]

Starting in 1699, other members of the Royal Society (of which Newton was a member) accused Leibniz of plagiarism, and the dispute broke out in full force in 1711. The Royal Society proclaimed in a study that it was Newton who was the true discoverer and labelled Leibniz a fraud. This study was cast into doubt when it was later found that Newton himself wrote the study's concluding remarks on Leibniz. Thus began the bitter controversy which marred the lives of both Newton and Leibniz until the latter's death in 1716.[34]

Newton is generally credited with the generalised binomial theorem, valid for any exponent. He discovered Newton's identities, Newton's method, classified cubic plane curves (polynomials of degree three in two variables), made substantial contributions to the theory of finite differences, and was the first to use fractional indices and to employ coordinate geometry to derive solutions to Diophantine equations. He approximated partial sums of the harmonic series by logarithms (a precursor to Euler's summation formula), and was the first to use power series with confidence and to revert power series.

He was appointed Lucasian Professor of Mathematics in 1669 on Barrow's recommendation. In that day, any fellow of Cambridge or Oxford was required to become an ordained Anglican priest. However, the terms of the Lucasian professorship required that the holder not be active in the church (presumably so as to have more time for science). Newton argued that this should exempt him from the ordination requirement, and Charles II, whose permission was needed, accepted this argument. Thus a conflict between Newton's religious views and Anglican orthodoxy was averted.[35]

Optics

A replica of Newton's second Reflecting telescope that he presented to the Royal Society in 1672[36]

From 1670 to 1672, Newton lectured on optics.[37] During this period he investigated the refraction of light, demonstrating that a prism could decompose white light into a spectrum of colours, and that a lens and a second prism could recompose the multicoloured spectrum into white light.[38]

He also showed that the coloured light does not change its properties by separating out a coloured beam and shining it on various objects. Newton noted that regardless of whether it was reflected or scattered or transmitted, it stayed the same colour. Thus, he observed that colour is the result of objects interacting with already-coloured light rather than objects generating the colour themselves. This is known as Newton's theory of colour.[39]

From this work, he concluded that the lens of any refracting telescope would suffer from the dispersion of light into colours (chromatic aberration). As a proof of the concept, he constructed a telescope using a mirror as the objective to bypass that problem.[40] Building the design, the first known functional reflecting telescope, today known as a Newtonian telescope,[40] involved solving the problem of a suitable mirror material and shaping technique. Newton ground his own mirrors out of a custom composition of highly reflective speculum metal, using Newton's rings to judge the quality of the optics for his telescopes. In late 1668[41] he was able to produce this first reflecting telescope. In 1671, the Royal Society asked for a demonstration of his reflecting telescope.[42] Their interest encouraged him to publish his notes On Colour, which he later expanded into his Opticks. When Robert Hooke criticised some of Newton's ideas, Newton was so offended that he withdrew from public debate. Newton and Hooke had brief exchanges in 1679–80, when Hooke, appointed to manage the Royal Society's correspondence, opened up a correspondence intended to elicit contributions from Newton to Royal Society transactions,[43] which had the effect of stimulating Newton to work out a proof that the elliptical form of planetary orbits would result from a centripetal force inversely proportional to the square of the radius vector (see Newton's law of universal gravitation – History and De motu corporum in gyrum). But the two men remained generally on poor terms until Hooke's death.[44]

Newton argued that light is composed of particles or corpuscles, which were refracted by accelerating into a denser medium. He verged on soundlike waves to explain the repeated pattern of reflection and transmission by thin films (Opticks Bk.II, Props. 12), but still retained his theory of ‘fits’ that disposed corpuscles to be reflected or transmitted (Props.13). Later physicists instead favoured a purely wavelike explanation of light to account for the interference patterns, and the general phenomenon of diffraction. Today's quantum mechanics, photons and the idea of wave–particle duality bear only a minor resemblance to Newton's understanding of light.

In his Hypothesis of Light of 1675, Newton posited the existence of the ether to transmit forces between particles. The contact with the theosophist Henry More, revived his interest in alchemy. He replaced the ether with occult forces based on Hermetic ideas of attraction and repulsion between particles. John Maynard Keynes, who acquired many of Newton's writings on alchemy, stated that "Newton was not the first of the age of reason: He was the last of the magicians."[45] Newton's interest in alchemy cannot be isolated from his contributions to science.[5] This was at a time when there was no clear distinction between alchemy and science. Had he not relied on the occult idea of action at a distance, across a vacuum, he might not have developed his theory of gravity. (See also Isaac Newton's occult studies.)

In 1704, Newton published Opticks, in which he expounded his corpuscular theory of light. He considered light to be made up of extremely subtle corpuscles, that ordinary matter was made of grosser corpuscles and speculated that through a kind of alchemical transmutation "Are not gross Bodies and Light convertible into one another, ...and may not Bodies receive much of their Activity from the Particles of Light which enter their Composition?"[46] Newton also constructed a primitive form of a frictional electrostatic generator, using a glass globe (Optics, 8th Query).

In an article entitled "Newton, prisms, and the 'opticks' of tunable lasers[47] it is indicated that Newton in his book Opticks was the first to show a diagram using a prism as a beam expander. In the same book he describes, via diagrams, the use of multiple-prism arrays. Some 278 years after Newton's discussion, multiple-prism beam expanders became central to the development of narrow-linewidth tunable lasers. Also, the use of these prismatic beam expanders led to the multiple-prism dispersion theory.[47]

Mechanics and gravitation

Newton's own copy of his Principia, with hand-written corrections for the second edition

Further information: Writing of Principia Mathematica

In 1679, Newton returned to his work on (celestial) mechanics, i.e., gravitation and its effect on the orbits of planets, with reference to Kepler's laws of planetary motion. This followed stimulation by a brief exchange of letters in 1679–80 with Hooke, who had been appointed to manage the Royal Society's correspondence, and who opened a correspondence intended to elicit contributions from Newton to Royal Society transactions.[43] Newton's reawakening interest in astronomical matters received further stimulus by the appearance of a comet in the winter of 1680–1681, on which he corresponded with John Flamsteed.[48] After the exchanges with Hooke, Newton worked out a proof that the elliptical form of planetary orbits would result from a centripetal force inversely proportional to the square of the radius vector (see Newton's law of universal gravitation – History and De motu corporum in gyrum). Newton communicated his results to Edmond Halley and to the Royal Society in De motu corporum in gyrum, a tract written on about 9 sheets which was copied into the Royal Society's Register Book in December 1684.[49] This tract contained the nucleus that Newton developed and expanded to form the Principia.

The Principia was published on 5 July 1687 with encouragement and financial help from Edmond Halley. In this work, Newton stated the three universal laws of motion that enabled many of the advances of the Industrial Revolution which soon followed and were not to be improved upon for more than 200 years, and are still the underpinnings of the non-relativistic technologies of the modern world. He used the Latin word gravitas (weight) for the effect that would become known as gravity, and defined the law of universal gravitation.

In the same work, Newton presented a calculus-like method of geometrical analysis by 'first and last ratios', gave the first analytical determination (based on Boyle's law) of the speed of sound in air, inferred the oblateness of the spheroidal figure of the Earth, accounted for the precession of the equinoxes as a result of the Moon's gravitational attraction on the Earth's oblateness, initiated the gravitational study of the irregularities in the motion of the moon, provided a theory for the determination of the orbits of comets, and much more.

Newton made clear his heliocentric view of the solar system – developed in a somewhat modern way, because already in the mid-1680s he recognised the "deviation of the Sun" from the centre of gravity of the solar system.[50] For Newton, it was not precisely the centre of the Sun or any other body that could be considered at rest, but rather "the common centre of gravity of the Earth, the Sun and all the Planets is to be esteem'd the Centre of the World", and this centre of gravity "either is at rest or moves uniformly forward in a right line" (Newton adopted the "at rest" alternative in view of common consent that the centre, wherever it was, was at rest).[51]

Newton's postulate of an invisible force able to act over vast distances led to him being criticised for introducing "occult agencies" into science.[52] Later, in the second edition of the Principia (1713), Newton firmly rejected such criticisms in a concluding General Scholium, writing that it was enough that the phenomena implied a gravitational attraction, as they did; but they did not so far indicate its cause, and it was both unnecessary and improper to frame hypotheses of things that were not implied by the phenomena. (Here Newton used what became his famous expression Hypotheses non fingo).

With the Principia, Newton became internationally recognised.[53] He acquired a circle of admirers, including the Swiss-born mathematician Nicolas Fatio de Duillier, with whom he formed an intense relationship that lasted until 1693, when it abruptly ended, at the same time that Newton suffered a nervous breakdown.[54]

Later life

Isaac Newton in old age in 1712, portrait by Sir James Thornhill

Main article: Later life of Isaac Newton

In the 1690s, Newton wrote a number of religious tracts dealing with the literal interpretation of the Bible. Henry More's belief in the Universe and rejection of Cartesian dualism may have influenced Newton's religious ideas. A manuscript he sent to John Locke in which he disputed the existence of the Trinity was never published. Later works – The Chronology of Ancient Kingdoms Amended (1728) and Observations Upon the Prophecies of Daniel and the Apocalypse of St. John (1733) – were published after his death. He also devoted a great deal of time to alchemy (see above).

Newton was also a member of the Parliament of England from 1689 to 1690 and in 1701, but according to some accounts his only comments were to complain about a cold draught in the chamber and request that the window be closed.[55]

Newton moved to London to take up the post of warden of the Royal Mint in 1696, a position that he had obtained through the patronage of Charles Montagu, 1st Earl of Halifax, then Chancellor of the Exchequer. He took charge of England's great recoining, somewhat treading on the toes of Lord Lucas, Governor of the Tower (and securing the job of deputy comptroller of the temporary Chester branch for Edmond Halley). Newton became perhaps the best-known Master of the Mint upon the death of Thomas Neale in 1699, a position Newton held for the last 30 years of his life.[56][57] These appointments were intended as sinecures, but Newton took them seriously, retiring from his Cambridge duties in 1701, and exercising his power to reform the currency and punish clippers and counterfeiters. As Master of the Mint in 1717 in the "Law of Queen Anne" Newton moved the Pound Sterling de facto from the silver standard to the gold standard by setting the bimetallic relationship between gold coins and the silver penny in favour of gold. This caused silver sterling coin to be melted and shipped out of Britain. Newton was made President of the Royal Society in 1703 and an associate of the French Académie des Sciences. In his position at the Royal Society, Newton made an enemy of John Flamsteed, the Astronomer Royal, by prematurely publishing Flamsteed's Historia Coelestis Britannica, which Newton had used in his studies.[58]

Personal coat of arms of Sir Isaac Newton[59]

In April 1705, Queen Anne knighted Newton during a royal visit to Trinity College, Cambridge. The knighthood is likely to have been motivated by political considerations connected with the Parliamentary election in May 1705, rather than any recognition of Newton's scientific work or services as Master of the Mint.[60] Newton was the second scientist to be knighted, after Sir Francis Bacon.

Towards the end of his life, Newton took up residence at Cranbury Park, near Winchester with his niece and her husband, until his death in 1727.[61] His half-niece, Catherine Barton Conduitt,[62] served as his hostess in social affairs at his house on Jermyn Street in London; he was her "very loving Uncle,"[63] according to his letter to her when she was recovering from smallpox.

Newton died in his sleep in London on 31 March 1727 [OS: 20 March 1726],[1] and was buried in Westminster Abbey. Newton, a bachelor, had divested much of his estate to relatives during his last years, and died intestate. After his death, Newton's hair was examined and found to contain mercury, probably resulting from his alchemical pursuits. Mercury poisoning could explain Newton's eccentricity in late life.[64]

After death

Fame

French mathematician Joseph-Louis Lagrange often said that Newton was the greatest genius who ever lived, and once added that Newton was also "the most fortunate, for we cannot find more than once a system of the world to establish."[65] English poet Alexander Pope was moved by Newton's accomplishments to write the famous epitaph:

Nature and nature's laws lay hid in night;

God said "Let Newton be" and all was light.

Newton himself had been rather more modest of his own achievements, famously writing in a letter to Robert Hooke in February 1676:

If I have seen further it is by standing on the shoulders of giants.[66]

Two writers think that the above quote, written at a time when Newton and Hooke were in dispute over optical discoveries, was an oblique attack on Hooke (said to have been short and hunchbacked), rather than – or in addition to – a statement of modesty.[67][68] On the other hand, the widely known proverb about standing on the shoulders of giants published among others by 17th-century poet George Herbert (a former orator of the University of Cambridge and fellow of Trinity College) in his Jacula Prudentum (1651), had as its main point that "a dwarf on a giant's shoulders sees farther of the two", and so its effect as an analogy would place Newton himself rather than Hooke as the 'dwarf'.

In a later memoir, Newton wrote:

I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.[69]

Albert Einstein kept a picture of Newton on his study wall alongside ones of Michael Faraday and James Clerk Maxwell.[70] Newton remains influential to today's scientists, as demonstrated by a 2005 survey of members of Britain's Royal Society (formerly headed by Newton) asking who had the greater effect on the history of science, Newton or Einstein. Royal Society scientists deemed Newton to have made the greater overall contribution.[71] In 1999, an opinion poll of 100 of today's leading physicists voted Einstein the "greatest physicist ever;" with Newton the runner-up, while a parallel survey of rank-and-file physicists by the site PhysicsWeb gave the top spot to Newton.[72]

Commemorations

Newton statue on display at the Oxford University Museum of Natural History

Newton's monument (1731) can be seen in Westminster Abbey, at the north of the entrance to the choir against the choir screen, near his tomb. It was executed by the sculptor Michael Rysbrack (1694–1770) in white and grey marble with design by the architect William Kent. The monument features a figure of Newton reclining on top of a sarcophagus, his right elbow resting on several of his great books and his left hand pointing to a scroll with a mathematical design. Above him is a pyramid and a celestial globe showing the signs of the Zodiac and the path of the comet of 1680. A relief panel depicts putti using instruments such as a telescope and prism.[73] The Latin inscription on the base translates as:

Here is buried Isaac Newton, Knight, who by a strength of mind almost divine, and mathematical principles peculiarly his own, explored the course and figures of the planets, the paths of comets, the tides of the sea, the dissimilarities in rays of light, and, what no other scholar has previously imagined, the properties of the colours thus produced. Diligent, sagacious and faithful, in his expositions of nature, antiquity and the holy Scriptures, he vindicated by his philosophy the majesty of God mighty and good, and expressed the simplicity of the Gospel in his manners. Mortals rejoice that there has existed such and so great an ornament of the human race! He was born on 25 December 1642, and died on 20 March 1726/7. — Translation from G.L. Smyth, The Monuments and Genii of St. Paul's Cathedral, and of Westminster Abbey (1826), ii, 703–4.[73]

From 1978 until 1988, an image of Newton designed by Harry Ecclestone appeared on Series D £1 banknotes issued by the Bank of England (the last £1 notes to be issued by the Bank of England). Newton was shown on the reverse of the notes holding a book and accompanied by a telescope, a prism and a map of the Solar System.[74]

A statue of Isaac Newton, looking at an apple at his feet, can be seen at the Oxford University Museum of Natural History.