In the scope of its subject, chemistry occupies an intermediate position between physics
It is sometimes called the central science
because it provides a foundation for understanding both basic
scientific disciplines at a fundamental level.
For example, chemistry explains aspects of plant chemistry (botany
), the formation of igneous rocks (geology
), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology
), the properties of the soil on the moon (cosmochemistry
), how medications work (pharmacology
), and how to collect DNA
evidence at a crime scene (forensics
The word chemistry
comes from a modification of the word alchemy,
which referred to an earlier set of practices that encompassed elements of chemistry, metallurgy
. Alchemy is often seen as linked to the quest to turn lead or other base metals into gold, though alchemists were also interested in many of the questions of modern chemistry.
The modern word alchemy
in turn is derived from the Arabic
(الكیمیاء). This may have Egyptian
origins since al-kīmīā
is derived from the Greek χημία, which is in turn derived from the word Kemet
, which is the ancient name of Egypt in the Egyptian language.
may derive from χημεία, meaning "cast together".
The current model of atomic structure is the quantum mechanical model
Traditional chemistry starts with the study of elementary particles
and other aggregates of matter
. Matter can be studied in solid, liquid, gas and plasma states
, in isolation or in combination. The interactions
and transformations that are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. Such behaviors are studied in a chemistry laboratory
The chemistry laboratory stereotypically uses various forms of laboratory glassware
. However glassware is not central to chemistry, and a great deal of experimental (as well as applied/industrial) chemistry is done without it.
A chemical reaction
is a transformation of some substances into one or more different substances.
The basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation
, which usually involves atoms as subjects. The number of atoms on the left and the right in the equation for a chemical transformation is equal. (When the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction
or radioactive decay
.) The type 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
In chemistry, matter is defined as anything that has rest mass
(it takes up space) and is made up of particles
. The particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon
. Matter can be a pure chemical substance
or a mixture
The atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus
surrounded by a space occupied by an electron cloud
. The nucleus is made up of positively charged protons
and uncharged neutrons
(together called nucleons
), while the electron cloud consists of negatively charged electrons
which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons. The nucleus is dense; the mass of a nucleon is approximately 1,836 times that of an electron, yet the radius of an atom is about 10,000 times that of its nucleus.
Standard form of the periodic table
of chemical elements. The colors represent different categories of elements
A chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons
in the nuclei of its atoms, known as the atomic number
and represented by the symbol Z
. The mass number
is the sum of the number of protons and neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number; atoms of an element which have different mass numbers are known as isotopes
. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon
, but atoms of carbon may have mass numbers of 12 or 13.
The standard presentation of the chemical elements is in the periodic table
, which orders elements by atomic number. The periodic table is arranged in groups
, or columns, and periods
, or rows. The periodic table is useful in identifying periodic trends
A ball-and-stick representation of the caffeine
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. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). 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
Thus, molecules exist as electrically neutral units, unlike ions. When this rule is broken, giving the "molecule" a charge, the result is sometimes named a molecular ion
or a polyatomic ion. However, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well-separated form, such as a directed beam in a vacuum in a mass spectrometer
. Charged polyatomic collections residing in solids (for example, common sulfate or nitrate ions) are generally not considered "molecules" in chemistry. Some molecules contain one or more unpaired electrons, creating radicals
. Most radicals are comparatively reactive, but some, such as nitric oxide (NO) can be stable.
The "inert" or noble gas elements
) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. Identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals
However, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that make up the solid crust, mantle, and core of the Earth are chemical compounds without molecules. These 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. Examples of such substances are mineral salts (such as table salt
), solids like carbon and diamond, metals, and familiar silica
and silicate minerals
such as quartz and granite.
One of the main characteristics 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.
Substance and mixture
Mole and amount of substance
Diagram showing relationships among the phases and the terms used to describe phase changes.
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
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
, 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).
An animation of the process of ionic bonding between sodium
(Na) and chlorine
(Cl) to form sodium chloride
, or common table salt. Ionic bonding involves one atom taking valence electrons from another (as opposed to sharing, which occurs in covalent bonding)
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.
An ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non-metal atom, becoming a negatively charged anion. The two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. For example, sodium
(Na), a metal, loses one electron to become an Na+
cation while chlorine
(Cl), a non-metal, gains this electron to become Cl−
. The ions are held together due to electrostatic attraction, and that compound sodium chloride
(NaCl), or common table salt, is formed.
In the methane
), the carbon atom shares a pair of valence electrons with each of the four hydrogen atoms. Thus, the octet rule is satisfied for C-atom (it has eight electrons in its valence shell) and the duet rule is satisfied for the H-atoms (they have two electrons in their valence shells).
In a covalent bond, one or more pairs of valence electrons
are shared by two atoms: the resulting electrically neutral group of bonded atoms is termed a molecule
. Atoms will share valence electrons in such a way as to create a noble gas
electron configuration (eight electrons in their outermost shell) for each atom. Atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule
. However, some elements like hydrogen
need only two electrons in their outermost shell to attain this stable configuration; these atoms are said to follow the duet rule
, and in this way they are reaching the electron configuration of the noble gas helium
, which has two electrons in its outer shell.
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.
In the context of chemistry, energy is an attribute of a substance as a consequence of its atomic
or aggregate structure
. Since a chemical transformation is accompanied by a change in one or more of these kinds of structures, it is invariably accompanied by an increase
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
– that is the probability of a 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 to occur 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
; 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 (H2
O); a liquid at room temperature because its molecules are bound by hydrogen bonds
Whereas hydrogen sulfide
S) 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
, etc. Spectroscopy is also used to identify the composition of remote objects – like stars and distant galaxies – by analyzing their radiation spectra.
Emission spectrum of iron
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.
During chemical reactions, bonds between atoms break and form, resulting in different substances with different properties. In a blast furnace, iron oxide, a compound
, reacts with carbon monoxide to form iron, one of the chemical elements
, and carbon dioxide.
When a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. A 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 as with the system environment, which may be designed vessels—often laboratory glassware
Chemical reactions can result in the formation or dissociation
of molecules, that is, molecules breaking apart to form two or more molecules or rearrangement of atoms within or across molecules. Chemical reactions usually involve the making or breaking of chemical bonds. Oxidation, reduction
, 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 in 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').
Ions and salts
The crystal lattice structure of potassium chloride
(KCl), a salt which is formed due to the attraction of K+
cations and Cl−
anions. Note how the overall charge of the ionic compound is zero.
is a charged species, an atom or a molecule, that has lost or gained one or more electrons. When an atom loses an electron and thus has more protons than electrons, the atom is a positively charged ion or cation
. When an atom gains an electron and thus has more electrons than protons, the atom is a negatively charged ion or anion
. Cations and anions can form a crystalline lattice of neutral salts
, such as the Na+
ions forming sodium chloride
, or NaCl. Examples of polyatomic ions
that do not split up during acid–base reactions
) and phosphate
is composed of gaseous matter that has been completely ionized, usually through high temperature.
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 that 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 this theory, 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
), which measures 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 Ka
are more likely to donate hydrogen ions in chemical reactions than those with lower Ka
idation) reactions include all chemical reactions
in which atoms have their oxidation state
changed by either gaining electrons (reduction) or losing electrons (oxidation). 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.
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, as 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.
Chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. Some of them are:
- Avogadro's law
- Beer–Lambert law
- Boyle's law (1662, relating pressure and volume)
- Charles's law (1787, relating volume and temperature)
- Fick's laws of diffusion
- Gay-Lussac's law (1809, relating pressure and temperature)
- Le Chatelier's principle
- Henry's law
- Hess's law
- Law of conservation of energy leads to the important concepts of equilibrium, thermodynamics, and kinetics.
- Law of conservation of mass continues to be conserved in isolated systems, even in modern physics. However, special relativity shows that due to mass–energy equivalence, whenever non-material "energy" (heat, light, kinetic energy) is removed from a non-isolated system, some mass will be lost with it. High energy losses result in loss of weighable amounts of mass, an important topic in nuclear chemistry.
- Law of definite composition, although in many systems (notably biomacromolecules and minerals) the ratios tend to require large numbers, and are frequently represented as a fraction.
- Law of multiple proportions
- Raoult's law
The history of chemistry
spans a period from very old times to the present. Since several millennia BC, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. Examples include extracting metals
, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into soap
, making glass
, and making alloys
. Chemistry was preceded by its protoscience, alchemy
, which is an intuitive but non-scientific approach to understanding the constituents of matter and their interactions. It was unsuccessful in explaining the nature of matter and its transformations, but, by performing experiments and recording the results, alchemists set the stage for modern chemistry. Chemistry as a body of knowledge distinct from alchemy began to emerge when a clear differentiation was made between them by Robert Boyle
in his work The Sceptical Chymist
(1661). While both alchemy and chemistry are concerned with matter and its transformations, the crucial difference was given by the scientific method
employed in their work. Chemistry is considered to have become an established science with the work of Antoine Lavoisier
, who developed a law of conservation of mass
that demanded careful measurement and quantitative observations of chemical phenomena. The history of chemistry is intertwined with the history of thermodynamics
, especially through the work of Willard Gibbs
The definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term "chymistry", in the view of noted scientist Robert Boyle
in 1661, meant the subject of the material principles of mixed bodies.
In 1663, the chemist Christopher Glaser
described "chymistry" as 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.
The 1730 definition of the word "chemistry", as used by Georg Ernst Stahl
, meant the art of resolving mixed, compound, or aggregate bodies into their principles; and of composing such bodies from those principles.
In 1837, Jean-Baptiste Dumas
considered the word "chemistry" to refer to the science concerned with the laws and effects of molecular forces.
This definition further evolved until, in 1947, it came to mean the science of substances: their structure, their properties, and the reactions that change them into other substances – a characterization accepted by Linus Pauling
More recently, in 1998, Professor Raymond Chang
broadened the definition of "chemistry" to mean the study of matter and the changes it undergoes.
Early civilizations, such as the EgyptiansBabylonians
amassed practical knowledge concerning the arts of metallurgy, pottery and dyes, but didn't develop a systematic theory.
A basic chemical hypothesis first emerged in Classical Greece
with the theory of four elements
as propounded definitively by Aristotle
stating that fire
were the fundamental elements from which everything is formed as a combination. Greek atomism
dates back to 440 BC, arising in works by philosophers such as Democritus
. In 50 BCE, the Roman
expanded upon the theory in his book De rerum natura
(On The Nature of Things).
Unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments.
An early form of the idea of conservation of mass
is the notion that "Nothing comes from nothing
" in Ancient Greek philosophy
, which can be found in Empedocles
(approx. 4th century BC): "For it is impossible for anything to come to be from what is not, and it cannot be brought about or heard of that what is should be utterly destroyed."
(3rd century BC), who, describing the nature of the Universe, wrote that "the totality of things was always such as it is now, and always will be".
In the Hellenistic world
the art of alchemy first proliferated, mingling magic and occultism into the study of natural substances with the ultimate goal of transmuting elements into gold
and discovering the elixir of eternal life.
Work, particularly the development of distillation
, continued in the early Byzantine
period with the most famous practitioner being the 4th century Greek-Egyptian Zosimos of Panopolis
Alchemy continued to be developed and practised throughout the Arab world
after the Muslim conquests
and from there, and from the Byzantine remnants,
diffused into medieval and Renaissance
Europe through Latin translations.
The development of the modern scientific method
was slow and arduous, but an early scientific method for chemistry began emerging among early Muslim chemists, beginning with the 9th century Perso-Arab chemist Jābir ibn Hayyān
, popularly known as "the father of chemistry". The Arabic works attributed to him introduced a systematic classification of chemical substances, and provided instructions for deriving an inorganic compound (sal ammoniac
or ammonium chloride
) from organic substances
(such as plants, blood, and hair) by chemical means.
Some Arabic Jabirian works (e.g., the "Book of Mercy", and the "Book of Seventy") were later translated into Latin under the Latinized
and in 13th-century Europe an anonymous writer, usually referred to as pseudo-Geber
, started to produce alchemical and metallurgical writings under this name.
Later influential Muslim philosophers, such as Abū al-Rayhān al-Bīrūnī
disputed the theories of alchemy, particularly the theory of the transmutation of metals
Under the influence of the new empirical methods
propounded by Sir Francis Bacon
and others, a group of chemists at Oxford
, Robert Boyle
, Robert Hooke
and John Mayow
began to reshape the old alchemical traditions into a scientific discipline. Boyle in particular is regarded as the founding father of chemistry due to his most important work, the classic chemistry text The Sceptical Chymist
where the differentiation is made between the claims of alchemy and the empirical scientific discoveries of the new chemistry.
He formulated Boyle's law
, rejected the classical "four elements" and proposed a mechanistic alternative of atoms and chemical reactions
that could be subject to rigorous experiment.
The theory of phlogiston
(a substance at the root of all combustion) was propounded by the German Georg Ernst Stahl
in the early 18th century and was only overturned by the end of the century by the French chemist Antoine Lavoisier
, the chemical analogue of Newton in physics; who did more than any other to establish the new science on proper theoretical footing, by elucidating the principle of conservation of mass
and developing a new system of chemical nomenclature used to this day.
English scientist John Dalton
proposed the modern theory of atoms
; that all substances are composed of indivisible 'atoms' of matter and that different atoms have varying atomic weights.
In his periodic table, Dmitri Mendeleev
predicted the existence of 7 new elements,
and placed all 60 elements known at the time in their correct places.
At the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. In 1897, J.J. Thomson
of Cambridge University
discovered the electron
and soon after the French scientist Becquerel
as well as the couple Pierre
and Marie Curie
investigated the phenomenon of radioactivity
. In a series of pioneering scattering experiments Ernest Rutherford
at the University of Manchester
discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully transmuted
the first element by bombarding nitrogen
with alpha particles
The year 2011 was declared by the United Nations as the International Year of Chemistry.
It was an initiative of the International Union of Pure and Applied Chemistry, and of the United Nations Educational, Scientific, and Cultural Organization and involves chemical societies, academics, and institutions worldwide and relied on individual initiatives to organize local and regional activities.
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
), atmospheric chemistry
, chemical engineering
, chemical biology
, environmental chemistry
, flavor chemistry
, flow chemistry
, green chemistry
, history of chemistry
, hydrogenation chemistry
, marine chemistry
, materials science
, mathematical chemistry
, medicinal chemistry
, molecular biology
, molecular mechanics
, natural product chemistry
, organometallic chemistry
, physical organic chemistry
, polymer chemistry
, solid-state chemistry
, supramolecular chemistry
, surface chemistry
, synthetic chemistry
, and many others.
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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.
- Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. ISBN 978-0-19-850346-0.
- 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
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