concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.]] s with one another and energy.]]

Chemistry (the etymology of the word has been much disputed) is the science of matter and the changes it undergoes. The science of matter is also addressed by physics, but while physics takes a more general and fundamental approach, chemistry is more specialized, being concerned with the composition, behavior, structure, and properties of matter, as well as the changes it undergoes during chemical reactions. It is a physical science which studies various substances, atoms, molecules, crystals and other aggregates of matter whether in isolation or combination, and which incorporates the concepts of energy and entropy in relation to the spontaneity of chemical processes.

Disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, the study of inorganic matter; organic chemistry, the study of organic (carbon based) matter; biochemistry, the study of substances found in biological organisms; physical chemistry, the study of chemical processes using physical concepts such as thermodynamics and quantum mechanics; and analytical chemistry, the analysis of material samples to gain an understanding of their chemical composition and structure. Many more specialized disciplines have emerged in recent years, e.g. neurochemistry the chemical study of the nervous system (see subdisciplines).

Summary

Chemistry is the scientific study of interaction of chemical substances that are constituted of atoms or the subatomic particles: protons, electrons and neutrons. Atoms combine to produce molecules or crystals. Chemistry is often called "the central science" because it connects the other natural sciences such as astronomy, physics, material science, biology and geology.

The genesis of chemistry can be traced to certain practices, known as alchemy, which had been practiced for several millennia in various parts of the world, particularly the Middle East.

The structure of objects we commonly use and the properties of the matter we commonly interact with are a consequence of the properties of chemical substances and their interactions. For example, steel is harder than iron because its atoms are bound together in a more rigid crystalline lattice; wood burns or undergoes rapid oxidation because it can react spontaneously with oxygen in a chemical reaction above a certain temperature; sugar and salt dissolve in water because their molecular/ionic properties are such that dissolution is preferred under the ambient conditions.

The transformations that are studied in chemistry are a result of interaction either between different chemical substances or between matter and energy. Traditional chemistry involves study of interactions between substances in a chemistry laboratory using various forms of laboratory glassware. , Institute of Biochemistry, University of Cologne]] A chemical reaction is a transformation of some substances into one or more other substances. It can be symbolically depicted through a chemical equation. The number of atoms on the left and the right in the equation for a chemical transformation is most often equal. The nature of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.

Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase as well as their chemical compositions. They can be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. Most chemists specialize in one or more sub-disciplines.

History

Ancient Egyptians pioneered the art of synthetic "wet" chemistry up to 4,000 years ago. By 1000 BC ancient civilizations were using technologies that formed the basis of the various branches of chemistry such as; extracting metal from their ores, making pottery and glazes, fermenting beer and wine, making pigments for cosmetics and painting, extracting chemicals from plants for medicine and perfume, making cheese, dying cloth, tanning leather, rendering fat into soap, making glass, and making alloys like bronze. ' atomist philosophy was later adopted by Epicurus (341–270 BCE).]] The genesis of chemistry can be traced to the widely observed phenomenon of burning that led to metallurgy—the art and science of processing ores to get metals (e.g. metallurgy in ancient India). The greed for gold led to the discovery of the process for its purification, even though the underlying principles were not well understood—it was thought to be a transformation rather than purification. Many scholars in those days thought it reasonable to believe that there exist means for transforming cheaper (base) metals into gold. This gave way to alchemy and the search for the Philosopher's Stone which was believed to bring about such a transformation by mere touch.

Greek atomism dates back to 440 BC, as what might be indicated by the book De Rerum Natura (The Nature of Things) written by the Roman Lucretius in 50 BC. Much of the early development of purification methods is described by Pliny the Elder in his Naturalis Historia.

A tentative outline is as follows:

# Egyptian alchemy [3,000 BCE – 400 BCE], formulate early "element" theories such as the Ogdoad. # Greek alchemy [332 BCE – 642 CE], the Greek king Alexander the Great conquers Egypt and founds Alexandria, having the world's largest library, where scholars and wise men gather to study. # Arab alchemy [642 CE – 1200], the Muslim conquest of Egypt (primarily Alexandria); development of the Scientific Method by Alhazen and Jābir ibn Hayyān revolutionise the field of Chemistry. Jābir (Latin name Geber) accepted many of the ideas of Aristotle but also modified Aristotle's ideas. # European alchemy [1300 – present], Pseudo-Geber builds on Arabic chemistry. From the 12th century, major advances in the chemical arts shifted from Arab lands to western Europe. were medieval Arab and Persian scholars. They introduced precise observation and controlled experimentation into the field and discovered numerous Chemical substances.

The works of Jābir became more widely known in Europe through Latin translations by a pseudo-Geber in 14th century Spain, who also wrote some of his own books under the pen name "Geber". The contribution of Indian alchemists and metallurgists in the development of chemistry was also quite significant.

The emergence of chemistry in Europe was primarily due to the recurrent incidence of the plague and blights there during the so called Dark Ages. This gave rise to a need for medicines. It was thought that there exists a universal medicine called the Elixir of Life that can cure all diseases, but like the Philosopher's Stone, it was never found. is considered the "Father of Modern Chemistry".]] For some practitioners, alchemy was an intellectual pursuit, over time, they got better at it. Paracelsus (1493–1541), for example, rejected the 4-elemental theory and with only a vague understanding of his chemicals and medicines, formed a hybrid of alchemy and science in what was to be called iatrochemistry. Similarly, the influences of philosophers such as Sir Francis Bacon (1561–1626) and René Descartes (1596–1650), who demanded more rigor in mathematics and in removing bias from scientific observations, led to a scientific revolution. In chemistry, this began with Robert Boyle (1627–1691), who came up with an equation known as Boyle's Law about the characteristics of gaseous state.

Chemistry indeed came of age when Antoine Lavoisier (1743–1794), developed the theory of Conservation of mass in 1783; and the development of the Atomic Theory by John Dalton around 1800. The Law of Conservation of Mass resulted in the reformulation of chemistry based on this law and the oxygen theory of combustion, which was largely based on the work of Lavoisier. Lavoisier's fundamental contributions to chemistry were a result of a conscious effort to fit all experiments into the framework of a single theory. He established the consistent use of the chemical balance, used oxygen to overthrow the phlogiston theory, and developed a new system of chemical nomenclature and made contribution to the modern metric system. Lavoisier also worked to translate the archaic and technical language of chemistry into something that could be easily understood by the largely uneducated masses, leading to an increased public interest in chemistry. All these advances in chemistry led to what is usually called the chemical revolution. The contributions of Lavoisier led to what is now called modern chemistry—the chemistry that is studied in educational institutions all over the world. It is because of these and other contributions that Antoine Lavoisier is often celebrated as the "Father of Modern Chemistry". The later discovery of Friedrich Wöhler that many natural substances, organic compounds, can indeed be synthesized in a chemistry laboratory also helped the modern chemistry to mature from its infancy.

The discovery of the chemical elements has a long history from the days of alchemy and culminating in the discovery of the periodic table of the chemical elements by Dmitri Mendeleev (1834–1907) and later discoveries of some synthetic elements.

Etymology

The word chemistry comes from the earlier study of alchemy, which is a set of practices that encompasses elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism and medicine. Alchemy in turn is derived from the Arabic word "كيمياء" meaning "value"; it is commonly thought of as the quest to turn lead or another common starting material into gold. This linguistic relation between the pursuit of value and alchemy is thought to have Egyptian origins. Many believe that the Arabic word "alchemy" is derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian. The word was subsequently borrowed by the Greeks, and from the Greeks by the Arabs when they occupied Alexandria (Egypt) in the 7th century. The Arabs added the Arabic definite article "al" to the word, resulting in the word "الكيمياء" (al-kīmiyā). Thus, 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 seems to invariably change per decade, 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). Chymistry (1661) – the subject of the material principles of mixt bodies (Boyle). 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). Chemistry (1730) – the art of resolving mixt, compound, or aggregate bodies into their principles; and of composing such bodies from those principles (Stahl). Chemistry (1837) – the science concerned with the laws and effects of molecular forces (Dumas). Chemistry (1947) – the science of substances: their structure, their properties, and the reactions that change them into other substances (Pauling). Chemistry (1998) – the study of matter and the changes it undergoes (Chang).

Basic concepts

Several concepts are essential for the study of chemistry; some of them are:

Atom

An atom is the basic unit of chemistry. It consists of a positively charged core (the atomic nucleus) which contains protons and neutrons, and which maintains a number of electrons to balance the positive charge in the nucleus. The atom is also the smallest entity that can be envisaged to retain some of the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state(s), coordination number, and preferred types of bonds to form (e.g., metallic, ionic, covalent).

Element

The concept of chemical element is related to that of chemical substance. A chemical element is specifically a substance which is composed of a single type of atom. A chemical element is characterized by a particular number of protons in the nuclei of its atoms. This number is known as the atomic number of the element. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, and all atoms with 92 protons in their nuclei are atoms of the element uranium. 94 different chemical elements or types of atoms based on the number of protons exist naturally. A further 18 have been recognised by IUPAC as existing artificially only. Although all the nuclei of all atoms belonging to one element will have the same number of protons, they may not necessarily have the same number of neutrons; such atoms are termed isotopes. In fact several isotopes of an element may exist.

The most convenient presentation of the chemical elements is in the periodic table of the chemical elements, which groups elements by atomic number. Due to its ingenious arrangement, groups, or columns, and periods, or rows, of elements in the table either share several chemical properties, or follow a certain trend in characteristics such as atomic radius, electronegativity, etc. Lists of the elements by name, by symbol, and by atomic number are also available.

Compound

A compound is a substance with a particular ratio of atoms of particular chemical elements which determines its composition, and a particular organization which determines chemical properties. For example, water is a compound containing hydrogen and oxygen in the ratio of two to one, with the oxygen atom between the two hydrogen atoms, and an angle of 104.5° between them. Compounds are formed and interconverted by chemical reactions.

Substance

A chemical substance is a kind of matter with a definite composition and set of properties. Strictly speaking, a mixture of compounds, elements or compounds and elements is not a chemical substance, but it may be called a chemical. Most of the substances we encounter in our daily life are some kind of mixture; for example: air, alloys, biomass, etc.

Nomenclature of substances is a critical part of the language of chemistry. Generally it refers to a system for naming chemical compounds. Earlier in the history of chemistry substances were given name by their discoverer, which often led to some confusion and difficulty. However, today the IUPAC system of chemical nomenclature allows chemists to specify by name specific compounds amongst the vast variety of possible chemicals. The standard nomenclature of chemical substances is set by the International Union of Pure and Applied Chemistry (IUPAC). There are well-defined systems in place for naming chemical species. Organic compounds are named according to the organic nomenclature system. Inorganic compounds are named according to the inorganic nomenclature system. In addition the Chemical Abstracts Service has devised a method to index chemical substance. In this scheme each chemical substance is identifiable by a number known as CAS registry number.

Molecule

A molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. Molecules can exist as electrically neutral units unlike ions. Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. shown here]]

Not all substances consist of discrete molecules. Most chemical elements are composed of lone atoms as their smallest discrete unit. Other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. Instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance; as they lack identifiable molecules.

One of the main characteristic of a molecule is its geometry often called its structure. While the structure of diatomic, triatomic or tetra atomic molecules may be trivial, (linear, angular pyramidal etc.) the structure of polyatomic molecules, that are constituted of more than six atoms (of several elements) can be crucial for its chemical nature.

Mole and amount of substance

Mole is a unit to measure amount of substance (also called chemical amount). A mole is the amount of a substance that contains as many elementary entities (atoms, molecules or ions) as there are atoms in 0.012 kilogram (or 12 grams) of carbon-12, where the carbon-12 atoms are unbound, at rest and in their ground state. The number of entities per mole is known as the Avogadro constant, and is determined empirically. The currently accepted value is 6.02214179(30) mol⁻¹ (2007 CODATA). One way to understand the meaning of the term "mole" is to compare and contrast it to terms such as dozen. Just as one dozen eggs contains 12 individual eggs, one mole contains 6.02214179(30) atoms, molecules or other particles. The term is used because it is much easier to say, for example, 1 mole of carbon, than it is to say 6.02214179(30) carbon atoms, and because moles of chemicals represent a scale that is easy to experience.

The amount of substance of a solute per volume of solution is known as amount of substance concentration, or molarity for short. Molarity is the quantity most commonly used to express the concentration of a solution in the chemical laboratory. The most commonly used units for molarity are mol/L (the official SI units are mol/m³).

Ions and salts

An ion is a charged species, an atom or a molecule, that has lost or gained one or more electrons. Positively charged cations (e.g. sodium cation Na⁺) and negatively charged anions (e.g. chloride Cl⁻) can form a crystalline lattice of neutral salts (e.g. sodium chloride NaCl). Examples of polyatomic ions that do not split up during acid-base reactions are hydroxide (OH⁻) and phosphate (PO₄³⁻).

Ions in the gaseous phase are often known as plasma.

Acidity and basicity

A substance can often be classified as an acid or a base. There are several different theories which explain acid-base behavior. The simplest is Arrhenius theory, which states than an acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water. According to Brønsted–Lowry acid-base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction; by extension, a base is the substance which receives that hydrogen ion. A third common theory is Lewis acid-base theory, which is based on the formation of new chemical bonds. Lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond. According to concept as per Lewis, the crucial things being exchanged are charges. There are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept

Acid strength is commonly measured by two methods. One measurement, based on the Arrhenius definition of acidity, is pH, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. Thus, solutions that have a low pH have a high hydronium ion concentration, and can be said to be more acidic. The other measurement, based on the Brønsted–Lowry definition, is the acid dissociation constant (K_a), which measure the relative ability of a substance to act as an acid under the Brønsted–Lowry definition of an acid. That is, substances with a higher K_a are more likely to donate hydrogen ions in chemical reactions than those with lower K_a values.

Phase

In addition to the specific chemical properties that distinguish different chemical classifications chemicals can exist in several phases. For the most part, the chemical classifications are independent of these bulk phase classifications; however, some more exotic phases are incompatible with certain chemical properties. A phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. Physical properties, such as density and refractive index tend to fall within values characteristic of the phase. The phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions.

Sometimes the distinction between phases can be continuous instead of having a discrete boundary, in this case the matter is considered to be in a supercritical state. When three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions.

The most familiar examples of phases are solids, liquids, and gases. Many substances exhibit multiple solid phases. For example, there are three phases of solid iron (alpha, gamma, and delta) that vary based on temperature and pressure. A principal difference between solid phases is the crystal structure, or arrangement, of the atoms. Another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution (that is, in water). Less familiar phases include plasmas, Bose-Einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. While most familiar phases deal with three-dimensional systems, it is also possible to define analogs in two-dimensional systems, which has received attention for its relevance to systems in biology.

Redox

It is a concept related to the ability of atoms of various substances to lose or gain electrons. Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. An oxidant removes electrons from another substance. Similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. A reductant transfers electrons to another substance, and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor. Oxidation and reduction properly refer to a change in oxidation number—the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number.

Bonding

atomic and molecular orbitals]]

Atoms sticking together in molecules or crystals are said to be bonded with one another. A chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them. More than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom.

A chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of Van der Waals force. Each of these kind of bond is ascribed to some potential. These potentials create the interactions which hold atoms together in molecules or crystals. In many simple compounds, Valence Bond Theory, the Valence Shell Electron Pair Repulsion model (VSEPR), and the concept of oxidation number can be used to explain molecular structure and composition. Similarly, theories from classical physics can be used to predict many ionic structures. With more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. See diagram on electronic orbitals.

Reaction

When a chemical substance is transformed as a result of its interaction with another or energy, a chemical reaction is said to have occurred. Chemical reaction is therefore a concept related to the 'reaction' of a substance when it comes in close contact with another, whether as a mixture or a solution; exposure to some form of energy, or both. It results in some energy exchange between the constituents of the reaction as well with the system environment which may be a designed vessels which are often laboratory glassware. Chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more smaller molecules, or rearrangement of atoms within or across molecules. Chemical reactions usually involve the making or breaking of chemical bonds. Oxidation, reduction, dissociation, acid-base neutralization and molecular rearrangement are some of the commonly used kinds of chemical reactions.

A chemical reaction can be symbolically depicted through a chemical equation. While in a non-nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for a nuclear reaction this holds true only for the nuclear particles viz. protons and neutrons.

The sequence of steps in which the reorganization of chemical bonds may be taking place in the course of a chemical reaction is called its mechanism. A chemical reaction can be envisioned to take place in a number of steps, each of which may have a different speed. Many reaction intermediates with variable stability can thus be envisaged during the course of a reaction. Reaction mechanisms are proposed to explain the kinetics and the relative product mix of a reaction. Many physical chemists specialize in exploring and proposing the mechanisms of various chemical reactions. Several empirical rules, like the Woodward-Hoffmann rules often come handy while proposing a mechanism for a chemical reaction.

According to the IUPAC gold book a chemical reaction is a process that results in the interconversion of chemical species". Accordingly, a chemical reaction may be an elementary reaction or a stepwise reaction. An additional caveat is made, in that this definition includes cases where the interconversion of conformers is experimentally observable. Such detectable chemical reactions normally involve sets of molecular entities as indicated by this definition, but it is often conceptually convenient to use the term also for changes involving single molecular entities (i.e. 'microscopic chemical events').

Equilibrium

Although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible. For example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase. A system of chemical substances at equilibrium even though having an unchanging composition is most often not static; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. Thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time. Chemicals present in biological systems are invariably not at equilibrium; rather they are far from equilibrium.

Energy

In the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. Since a chemical transformation is accompanied by a change in one or more of these kinds of structure, it is invariably accompanied by an increase or decrease of energy of the substances involved. Some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light; thus the products of a reaction may have more or less energy than the reactants. A reaction is said to be exergonic if the final state is lower on the energy scale than the initial state; in the case of endergonic reactions the situation is the reverse. A reaction is said to be exothermic if the reaction releases heat to the surroundings; in the case of endothermic reactions, the reaction absorbs heat from the surroundings.

Chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. The speed of a chemical reaction (at given temperature T) is related to the activation energy E, by the Boltzmann's population factor $e^\{-E/kT\}$ - that is the probability of molecule to have energy greater than or equal to E at the given temperature T. This exponential dependence of a reaction rate on temperature is known as the Arrhenius equation. The activation energy necessary for a chemical reaction can be in the form of heat, light, electricity or mechanical force in the form of ultrasound.

A related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. A reaction is feasible only if the total change in the Gibbs free energy is negative, $\backslash Delta\; G\; \backslash le\; 0\; \backslash ,$; if it is equal to zero the chemical reaction is said to be at equilibrium.

There exist only limited possible states of energy for electrons, atoms and molecules. These are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. The atoms/molecules in a higher energy state are said to be excited. The molecules/atoms of substance in an excited energy state are often much more reactive; that is, more amenable to chemical reactions.

The phase of a substance is invariably determined by its energy and the energy of its surroundings. When the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water (H₂O); a liquid at room temperature because its molecules are bound by hydrogen bonds. Whereas hydrogen sulfide (H₂S) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole-dipole interactions.

The transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. However, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. Thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. For example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy.

The existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. Different kinds of spectra are often used in chemical spectroscopy, e.g. IR, microwave, NMR, ESR, etc. Spectroscopy is also used to identify the composition of remote objects - like stars and distant galaxies - by analyzing their radiation spectra.

The term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances.

Chemical laws

Chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. Some of them are:

Subdisciplines

Chemistry is typically divided into several major sub-disciplines. There are also several main cross-disciplinary and more specialized fields of chemistry.

Analytical chemistry is the analysis of material samples to gain an understanding of their chemical composition and structure. Analytical chemistry incorporates standardized experimental methods in chemistry. These methods may be used in all subdisciplines of chemistry, excluding purely theoretical chemistry.

Biochemistry is the study of the chemicals, chemical reactions and chemical interactions that take place in living organisms. Biochemistry and organic chemistry are closely related, as in medicinal chemistry or neurochemistry. Biochemistry is also associated with molecular biology and genetics.

Inorganic chemistry is the study of the properties and reactions of inorganic compounds. The distinction between organic and inorganic disciplines is not absolute and there is much overlap, most importantly in the sub-discipline of organometallic chemistry.

Materials chemistry is the preparation, characterization, and understanding of substances with a useful function. The field is a new breadth of study in graduate programs, and it integrates elements from all classical areas of chemistry with a focus on fundamental issues that are unique to materials. Primary systems of study include the chemistry of condensed phases (solids, liquids, polymers) and interfaces between different phases.

Neurochemistry is the study of neurochemicals; including transmitters, peptides, proteins, lipids, sugars, and nucleic acids; their interactions, and the roles they play in forming, maintaining, and modifying the nervous system.

Nuclear chemistry is the study of how subatomic particles come together and make nuclei. Modern Transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field.

Organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. An organic compound is defined as any compound based on a carbon skeleton.

Physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. In particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. Important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, spectroscopy, and more recently, astrochemistry. Physical chemistry has large overlap with molecular physics. Physical chemistry involves the use of infinitesimal calculus in deriving equations. It is usually associated with quantum chemistry and theoretical chemistry. Physical chemistry is a distinct discipline from chemical physics, but again, there is very strong overlap.

Theoretical chemistry is the study of chemistry via fundamental theoretical reasoning (usually within mathematics or physics). In particular the application of quantum mechanics to chemistry is called quantum chemistry. Since the end of the Second World War, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. Theoretical chemistry has large overlap with (theoretical and experimental) condensed matter physics and molecular physics.

Other fields include agrochemistry, astrochemistry (and cosmochemistry), atmospheric chemistry, chemical engineering, chemical biology, chemo-informatics, electrochemistry, environmental chemistry, femtochemistry, flavor chemistry, flow chemistry, geochemistry, green chemistry, histochemistry, history of chemistry, hydrogenation chemistry, immunochemistry, marine chemistry, materials science, mathematical chemistry, mechanochemistry, medicinal chemistry, molecular biology, molecular mechanics, nanotechnology, natural product chemistry, oenology, organometallic chemistry, petrochemistry, pharmacology, photochemistry, physical organic chemistry, phytochemistry, polymer chemistry, radiochemistry, solid-state chemistry, sonochemistry, supramolecular chemistry, surface chemistry, synthetic chemistry, thermochemistry, and many others.

Chemical industry

The chemical industry represents an important economic activity. The global top 50 chemical producers in 2004 had sales of 587 billion US dollars with a profit margin of 8.1% and research and development spending of 2.1% of total chemical sales.

Professional societies

American Chemical Society

American Society for Neurochemistry

Chemical Institute of Canada

Chemical Society of Peru

International Union of Pure and Applied Chemistry

Royal Australian Chemical Institute

Royal Netherlands Chemical Society

Royal Society of Chemistry

Society of Chemical Industry

World Association of Theoretical and Computational Chemists

Others

See also

Common chemicals

Philosophy of chemistry

International Year of Chemistry

List of chemistry topics

List of chemists

List of compounds

List of important publications in chemistry

List of software for molecular mechanics modeling

Periodic Table of the Elements

Timeline of chemistry

Unsolved problems in chemistry

References

Further reading

;Popular reading

Atkins, P.W. Galileo's Finger (Oxford University Press) ISBN 0-19-860941-8

Atkins, P.W. Atkins' Molecules (Cambridge University Press) ISBN 0-521-82397-8

Stwertka, A. A Guide to the Elements (Oxford University Press) ISBN 0-19-515027-9

;Introductory undergraduate text books

Atkins, P.W., Overton, T., Rourke, J., Weller, M. and Armstrong, F. Shriver and Atkins inorganic chemistry (4th edition) 2006 (Oxford University Press) ISBN 0-19-926463-5

Chang, Raymond. Chemistry 6th ed. Boston: James M. Smith, 1998. ISBN 0-07-115221-0.

Voet and Voet Biochemistry (Wiley) ISBN 0-471-58651-X

;Advanced undergraduate-level or graduate text books

Atkins, P.W. Physical Chemistry (Oxford University Press) ISBN 0-19-879285-9

Atkins, P.W. et al. Molecular Quantum Mechanics (Oxford University Press)

McWeeny, R. Coulson's Valence (Oxford Science Publications) ISBN 0-19-855144-4

Pauling, L. The Nature of the chemical bond (Cornell University Press) ISBN 0-8014-0333-2

Pauling, L., and Wilson, E. B. Introduction to Quantum Mechanics with Applications to Chemistry (Dover Publications) ISBN 0-486-64871-0

Smart and Moore Solid State Chemistry: An Introduction (Chapman and Hall) ISBN 0-412-40040-5

Stephenson, G. Mathematical Methods for Science Students (Longman) ISBN 0-582-44416-0

Category:Natural sciences

Name	Tom Lehrer
Background	solo_singer
Birth name	Thomas Andrew Lehrer
Born	April 09, 1928New York, New York
Instrument	VocalsPiano
Occupation	Mathematician, teacher, lyricist, pianist, composer, singer/songwriter
Years active	1945–1971, 1998
Label	Reprise/Warner Bros. RecordsRhino/Atlantic RecordsShout! Factory
Associated acts	Joe Raposo

Thomas Andrew "Tom" Lehrer (born April 9, 1928) is an American singer-songwriter, satirist, pianist, and mathematician. He has lectured on mathematics and musical theater. Lehrer is best known for the pithy, humorous songs he recorded in the 1950s and 1960s.

His work often parodies popular song forms, such as in "The Elements", where he sets the names of the chemical elements to the tune of the "Major-General's Song" from Gilbert and Sullivan's Pirates of Penzance. Lehrer's earlier work typically dealt with non-topical subject matter and was noted for its black humor, seen in songs such as "Poisoning Pigeons in the Park". In the 1960s, he produced a number of songs dealing with social and political issues of the day, particularly when he wrote for the U.S. version of the television show That Was The Week That Was.

In the early 1970s he retired from public performances to devote his time to teaching mathematics and music theatre at UCSC. He did two additional performances in 1998 at a London gala show celebrating the career of impresario Cameron Mackintosh.

Early life

Born in 1928 to a Jewish family in the Manhattan borough of New York City, Tom Lehrer began studying classical piano music at the age of seven, but was more interested in the popular music of the age. Eventually, his mother also sent him to a popular-music piano teacher. At this early age, he began writing his own show tunes, which eventually would help him in his future adventures as a satirical composer and writer in his years of lecturing at Harvard University and later at other universities.

Lehrer graduated from the Loomis Chaffee School in Windsor, Connecticut. He attended Camp Androscoggin both as a camper and a counselor. While studying mathematics as an undergraduate student at Harvard University, he began to write comic songs to entertain his friends, including "Fight Fiercely, Harvard" (1945). Those songs later were named The Physical Revue, a joking reference to a leading scientific journal, The Physical Review.

Mathematics career

Lehrer earned his AB in mathematics (magna cum laude) from Harvard University in 1947, when he was nineteen. He received his MA degree the next year and was inducted into Phi Beta Kappa. He taught classes at MIT, Harvard, and Wellesley.

He remained in Harvard's doctoral program for several years, taking time out for his musical career and to work as a researcher at Los Alamos, New Mexico. He served in the Army from 1955 to 1957, working at the National Security Agency. (Lehrer has stated that he invented the during this time, as a means of circumventing liquor restrictions.) All of these experiences eventually became fodder for songs, viz. "Fight Fiercely, Harvard", "The Wild West Is Where I Want To Be" and "It Makes a Fellow Proud to Be a Soldier". Despite holding a master's degree in an era when American conscripts often lacked a high school diploma, Lehrer served as an enlisted soldier, achieving the rank of Specialist Four, which he described as being a "Corporal without portfolio". In 1960, Lehrer returned to full-time studies at Harvard, but he never completed his doctoral studies in mathematics.

From 1962, he taught in the political science department at Massachusetts Institute of Technology (MIT). In 1972, he joined the faculty of the University of California, Santa Cruz, teaching an introductory course entitled "The Nature of Mathematics" to liberal arts majors—"Math for Tenors", according to Lehrer. He also taught a class in musical theater. He occasionally performed songs in his lectures, primarily those relating to the topic.

In 2001, Lehrer taught his last mathematics class (on the topic of infinity) and retired from academia. He has remained in the area, and still "hangs out" around the University of California, Santa Cruz.

Inspired by the success of his performances of his own songs, he paid for some studio time to record Songs by Tom Lehrer. At the time radio stations would not give Lehrer air time because of his controversial subjects. Instead, he sold his album on campus at Harvard for three dollars, while "supportive record merchants and dorm newsstands bought copies…and marked them up fifty cents." After one summer, he also started to receive mail orders from all parts of the country (as far away as San Francisco after The Chronicle wrote an article on the record). Interest in his recordings was spread by word of mouth; friends and supporters brought their records home and played them for their friends, who then also wanted a copy.

Self-published and without promotion, the album—which included the macabre "I Hold Your Hand in Mine", the mildly risqué "Be Prepared", and "Lobachevsky" (regarding plagiarizing mathematicians)—became a cult success via word of mouth. Lehrer then embarked on a series of concert tours and recorded a second album, which was released in two versions: the songs were the same, but More of Tom Lehrer was studio-recorded, while An Evening Wasted with Tom Lehrer was recorded live in concert.

Lehrer's major breakthrough in the United Kingdom came as a result of the citation accompanying an honorary degree given to Princess Margaret, where she cited musical tastes as "catholic, ranging from Mozart to Tom Lehrer". This prompted significant interest in his works and helped secure distributors for his material in the U.K. It was there that his music achieved real popularity, as a result of the proliferation of university newspapers referring to the material, and the willingness of the BBC to play his songs on the radio (something that was a rarity in the United States).

By the early 1960s, Lehrer had retired from touring (which he intensely disliked) and was employed as the resident songwriter for the U.S. edition of That Was The Week That Was (TW³), a satirical television show. An increased proportion of his output became overtly political, or at least topical, on subjects such as education ("New Math"), the Second Vatican Council ("The Vatican Rag"), race relations ("National Brotherhood Week"), air and water pollution ("Pollution"), American militarism ("Send the Marines"), World War III "pre-nostalgia" ("So Long, Mom", premiered by Steve Allen), and nuclear proliferation ("Who's Next?" and "MLF Lullaby"). He also wrote a song that famously satirized the alleged amorality of the rocket scientist, Wernher von Braun, who previously had worked for Nazi Germany before working for the United States. ("'Once the rockets are up, who cares where they come down? That's not my department', says Wernher von Braun.") Lehrer did not appear on the television show; his songs were performed by a female vocalist and his lyrics often were altered by the network censors. Lehrer later performed the songs on the album, That Was The Year That Was, so that, in his words, people could hear the songs the way they were intended to be heard.

In 1967, Lehrer was persuaded to make a short tour in Norway and Denmark, where he performed some of the songs from the television program. The performance in Oslo, Norway, on September 10 was recorded on video tape and aired locally later that autumn; this program was released on DVD some 40 years later.

Also around 1967, Lehrer composed and performed on piano original songs in a Dodge automobile "industrial" film that was distributed primarily to Dodge automobile dealers. It was also shown at promotional events organized by Dodge. Set in a fictional American wild west town, the full proper title of the film appears to be "The Dodge Rebellion Theatre presents Ballads For '67" Since the film is introducing 1967 model automobiles, it was possibly produced in late 1966.

The record deal with Reprise Records for the That Was The Year That Was album also gave Reprise distribution rights for Lehrer's earlier recordings, as Lehrer wanted to wind up his own record imprint. The Reprise issue of Songs by Tom Lehrer was a stereo re-recording. This version was not issued on CD, but the songs were issued on the live Tom Lehrer Revisited CD instead. The [live] recording also included bonus tracks "L-Y" and "Silent E", which Lehrer wrote for the PBS children's educational series The Electric Company. Lehrer later commented that worldwide sales of the recordings under Reprise surpassed 1.8 million units in 1996. That same year, the album That Was The Year That Was went gold. Another mistaken belief is that he was sued for libel by the estate of Wernher Von Braun, the subject of one of his songs, and forced to relinquish all of his royalty income to Von Braun. Lehrer firmly denied this in a 2003 interview.

When asked about his reasons for abandoning his musical career, in an interview in the book accompanying his CD box set (released in 2000), he cited a simple lack of interest, a distaste for touring, and boredom with performing the same songs repeatedly. He observed that when he was moved to write and perform songs, he did, and when he was not, he did not, and that after a while he simply lost interest. Although many of Lehrer's songs satirized the Cold War political establishment of the era, he stopped writing and performing just as the 1960s counterculture movement gained momentum.

Lehrer's musical career was brief; in an interview in the late 1990s, he pointed out that he had performed a mere 109 shows and written 37 songs over 20 years. Nevertheless, he developed a significant cult following both in the United States and abroad.

In the 1970s, Lehrer concentrated on teaching mathematics and musical theater, although he also wrote ten songs for the children's television show The Electric Company—Lehrer's Harvard schoolmate Joe Raposo was the show's musical director for its first three seasons.

Revivals and discographic reissues

In the early 1980s, Tom Foolery, a revival of his songs on the London stage, was a hit. Although not its instigator, Lehrer eventually gave the stage production his full support and updated several of his lyrics for the production (such as "Who's Next", in which Neiman-Marcus, not Alabama, gets the bomb). Tom Foolery contained 27 Lehrer songs and led to more than 200 productions,

In conjunction with the Tom Foolery premiere in 1980 at Criterion Theatre in London, Lehrer made a rare TV appearance on BBCs Parkinson show, where he sang "I Got It From Agnes".

On June 7 and 8, 1998, Lehrer performed in public for the first time in 25 years at the Lyceum Theatre, London as part of the gala show Hey, Mr. Producer! celebrating the career of impresario Cameron Mackintosh, who had been the producer of Tom Foolery. The June 8 show was his only performance before Queen Elizabeth II. Lehrer sang "Poisoning Pigeons in the Park" and an updated version of the nuclear proliferation song "Who's Next?". The DVD of the event includes the former song.

In 2000, a boxed set of CDs, The Remains of Tom Lehrer, was released by Rhino Entertainment. It included live and studio versions of his first two albums, That Was The Year That Was, the songs he wrote for The Electric Company, and some previously unreleased material. It was accompanied by a small hardbound book containing an introduction by Dr. Demento and lyrics to all the songs.

In 2010, Shout! Factory launched a reissue campaign, making his long out-of-press albums available digitally. They also issued a CD/DVD combo called The Tom Lehrer Collection, which includes his best-loved songs, plus a DVD featuring an Oslo concert.

Musical legacy

Lehrer has commented that he doubts his songs had any real effect on those not already critical of the establishment: "I don't think this kind of thing has an impact on the unconverted, frankly. It's not even preaching to the converted; it's titillating the converted... I'm fond of quoting Peter Cook, who talked about the satirical Berlin kabaretts of the 1930s, which did so much to stop the rise of Hitler and prevent the Second World War."

A play, Letters from Lehrer, written by Canadian Richard Greenblatt, was performed by him at CanStage, from January 16 to February 25, 2006. It followed Lehrer's musical career, the meaning of several songs, the politics of the time, and Greenblatt's own experiences with Lehrer's music, while playing some of Lehrer's songs. There are currently no plans for more performances, although low-quality audio recordings have begun to circulate around the internet.

Lehrer was praised by Dr. Demento as "the best musical satirist of the twentieth century". Other artists who cite Lehrer as an influence include "Weird Al" Yankovic, whose work generally addresses more popular and less technical or political subjects, and educator and scientist H. Paul Shuch, who tours under the stage name Dr. SETI and calls himself "a cross between Carl Sagan and Tom Lehrer: he sings like Sagan and lectures like Lehrer." More stylistically influenced performers include American political satirist Mark Russell, and the British duo Kit and The Widow. British medical satirists Amateur Transplants acknowledge the debt they owe to Tom Lehrer on the back of their first album, Fitness to Practice. Their songs "The Menstrual Rag" and "The Drugs Song" are to the tunes of Lehrer's "The Vatican Rag" and "The Elements" respectively. Their second album, Unfit to Practise, opens with an update of Lehrer's "The Masochism Tango" and is called simply "Masochism Tango 2008". Syndicated conservative morning-radio talk show host Jim Quinn sings with piano backing in a Lehrer-like tribute in a song on how political correctness has destroyed so many Christmas traditions with the song "A Politically Correct Christmas".

Lehrer has said of his musical career, "If, after hearing my songs, just one human being is inspired to say something nasty to a friend, or perhaps to strike a loved one, it will all have been worth the while."

Music lists

Reviews selected by Lehrer for his liner notes

"Mr. Lehrer's muse is not fettered by such inhibiting factors as taste." — The New York Times (9 February 1959)

"More desperate than amusing" — New York Herald Tribune

"He seldom has any point to make except obvious ones" — The Christian Science Monitor

"Plays the piano acceptably" — The Oakland Tribune

Solo discography

Songs by Tom Lehrer (1953)

More of Tom Lehrer (1959)

An Evening Wasted with Tom Lehrer (1959)

Tom Lehrer Revisited (1960) (1990 CD reissue includes 1971 studio recordings of Silent E and L-Y)

Tom Lehrer Discovers Australia (And Vice Versa) (1960; Australia-only)

That Was the Year That Was (1965)

Tom Lehrer in Concert (1994; UK compilation)

Songs & More Songs by Tom Lehrer (1997)

The Remains of Tom Lehrer (2000)

The Tom Lehrer Collection (2010)

Many Lehrer songs also are performed (but not by Lehrer) in That Was The Week That Was (Radiola LP, 1981)

The sheet music to many of Lehrer's songs is published in The Tom Lehrer Song Book (Crown Publishers, Inc., 1954) Library of Congress Card Catalog Number 54-12068 and (Pantheon, 1981, ISBN 0-394-74930-8).

References

External links

That Was the Wit That Was Tom Lehrer interview in SF Weekly, published 2000-04-19, retrieved 2010-08-26

59 minute long mp3 radio programme from 1983, with a telephone interview with Tom Lehrer, as well as a 10 minute follow-up 1989 From "Bob Claster's Funny Stuff" on KCRW, retrieved 2010-08-26

A Conversation with Tom Lehrer done by Paul D. Lehrman on September 7, 1997, retrieved 2010-08-26

Category:1928 births Category:Living people Category:20th-century mathematicians Category:American male singers Category:American mathematicians Category:American novelty song performers Category:American satirists Category:American singer-songwriters Category:American pianists Category:American comedy musicians Category:Harvard University alumni Category:Reprise Records artists Category:Massachusetts Institute of Technology faculty Category:Parody musicians Category:University of California, Santa Cruz faculty Category:Horace Mann School alumni Category:United States Army soldiers Category:Jewish songwriters Category:Wellesley College faculty Category:Jewish comedians Category:Jewish American military personnel