Chemistry (from
Arabic:الكيم
Latinized: chem (kēme), meaning
"earth") is the
science 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 for studies of various
atoms,
molecules,
crystals and other aggregates of matter
whether in isolation or combination, which incorporates the
concepts of
energy and
entropy in relation to the
spontaneity of
chemical processes. Modern chemistry
evolved out of
alchemy and began to develop
into its modern form through the 10th Century Arab world and
following the
chemical
revolution (1773).
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 matter;
biochemistry, the study of
substances found in
biological organisms;
physical chemistry, the
energy related studies of chemical systems at macro,
molecular and submolecular scales;
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.
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.
Chemistry is an integral part of the
science
curriculum both at the
high school as
well as the early college level. At these levels, it is often
called "
general chemistry" which
is an introduction to a wide variety of fundamental concepts that
enable the student to acquire tools and skills useful at the
advanced levels, whereby chemistry is invariably studied in any of
its various sub-disciplines.
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.
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.
The earliest pioneers of Chemistry, and inventors of the modern
scientific method, were medieval
Arab and Persian
scholars. They introduced precise
observation and controlled
experimentation into the field and discovered
numerous
Chemical
substances.
Will Durant (1980),
The Age of Faith (The Story of Civilization, Volume 4), p.
162-186, Simon & Schuster, ISBN 0671012002:
The most influential Muslim chemists were
Geber (d. 815),
al-Kindi (d.
873),
al-Razi (d. 925),
al-Biruni (d.
1048) and
Alhazen (d. 1039).Dr. K. Ajram
(1992),
Miracle of Islamic Science, Appendix B, Knowledge
House Publishers, ISBN 0911119434.
The works
of Geber 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.
Will Durant
(1935): Our Oriental Heritage: Simon & Schuster:
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.
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 creation 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 is commonly thought of as the quest to turn
lead or another common starting material into gold. As to the
origin of the word "alchemy" the question is a debatable one; it
certainly can be traced back to the Greeks, and some, following E.
Wallis Budge, have also asserted
Egyptian origins.
Many believe that the
word "alchemy" is derived from the word Chemi or
Kimi, which is the 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", from which is
derived the old French
alkemie. 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 Arabs invade Alexandria; Jabir is the main
chemist
- European alchemy [1300 – present], Pseudo-Geber builds on Arabic chemistry
- Chemistry [1661], Boyle writes his
classic chemistry text The Sceptical Chymist
- Chemistry [1787], Lavoisier
writes his classic Elements of Chemistry
- Chemistry [1803], Dalton publishes
his Atomic Theory
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 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. However, several
isotopes of an element, that differ from one another
in the number of neutrons present in the nucleus, 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 infinite 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 numeric number known as
CAS registry number.
Molecule
A
molecule is the smallest indivisible portion, besides an
atom, 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.
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
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. This number is known as the
Avogadro constant, and is
determined empirically. The currently accepted value is
6.02214179(30) mol
−1 (2007
CODATA). The best way to understand the meaning of
the term "mole" is to compare it to terms such as
dozen. Just as one dozen is equal to 12, one mole is
equal to 6.02214179(30) . The term is used because it is much
easier to say, for example, 1 mole of carbon atoms, than it is to
say 6.02214179(30) carbon atoms. Likewise, we can describe the
number of entities as a multiple or fraction of 1 mole, e.g. 2 mole
or 0.5 moles. Mole is an absolute number (having no units) and can
describe any type of elementary object, although the mole's use is
usually limited to measurement of
subatomic,
atomic, and
molecular structures.
The number of moles of a substance in one liter of a
solution is known as its
molarity. Molarity is the common unit used to
express the
concentration of a
solution in
physical
chemistry.
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
salt (e.g.
sodium chloride NaCl). Examples of
polyatomic ions that do not split up during
acid-base reactions are
hydroxide (OH
−) and
phosphate (PO
43−).
Ions in the gaseous phase is often known as
plasma.
Acidity and basicity
A substance can often be classified as an
acid
or a
base. This is often done on
the basis of a particular kind of reaction, namely the exchange of
protons between chemical compounds. However, an extension to this
mode of classification was brewed up by the American chemist,
Gilbert Newton Lewis; in this
mode of classification the reaction is not limited to those
occurring in an
aqueous solution,
thus is no longer limited to solutions in water. 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
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, whihch 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.
Chemical bond
A
chemical bond is a concept for understanding how atoms
stick together in molecules. It 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. 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 predict 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 fails and alternative
approaches, primarily based on principles of
quantum chemistry such as the
molecular orbital theory, are necessary.
See diagram on electronic orbitals.
Chemical reaction
Chemical reaction is a concept related to the
transformation of a
chemical
substance through its interaction with another, or as a result
of its interaction with some
form of
energy. A chemical reaction may occur naturally or carried out
in a laboratory by chemists in specially designed vessels which are
often
laboratory glassware. It
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.
A stricter definition is that "a chemical reaction is a process
that results in the interconversion of chemical species". Under
this definition, 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').
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
exothermic if the final state is lower on the
energy scale than the initial state; in the case of
endothermic reactions the situation is
otherwise.
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, \Delta G
\le 0 \,; 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 (H
2O); a
liquid at room temperature because its molecules are bound by
hydrogen bonds. Whereas
hydrogen sulfide (H
2S) 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, and spectroscopy. 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.
- 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,
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,
neurochemistry,
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
See also
References
Further reading
- Popular reading
- Atkins, P.W. Galileo's Finger (Oxford University Press) ISBN
0198609418
- Atkins, P.W. Atkins' Molecules (Cambridge University
Press) ISBN 0521823978
- Stwertka, A. A Guide to the Elements (Oxford
University Press) ISBN 0195150279
- 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
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