Branches of Chemistry

Chemists have divided chemistry into a number of different branches. These branches are somewhat arbitrary and do not have sharply defined boundaries. They often overlap with each other or with other sciences, such as physics, geology, or biology.

Inorganic chemistry is the study of the chemical nature of the elements and their compounds (except hydrocarbons—compounds composed of carbon and hydrogen).

Organic chemistry is the study of compounds consisting largely of hydrocarbons, which provide the parent material of all other organic compounds. Since carbon atoms can form rings and long branched chains, hundreds of thousands of carbon-based molecules exist. Organic compounds are of special importance, because they make up the majority of compounds in living organisms. Organic compounds form coal and petroleum. Organic chemists have learned how to convert raw materials from coal, petroleum, and grain into synthetic textiles, pesticides, dyes, drugs, plastics, and many other products.

Radiochemistry is the study of the chemical effects of high-energy radiation and the behavior of radioactive isotopes, atoms of the same element that vary in the number of neutrons they contain. For example, the heaviest known element, Element 112 (ununbium, or Uub) was first created by scientists at the Heavy-Ion Research Laboratory in Darmstadt, Germany in 1996. These scientists created an atom of ununbium containing 165 neutrons, labeled ununbium-277 (112 protons + 165 neutrons = ununbium-277). Because the ununbium nucleus contains so many particles, the atom becomes unstable and splits into smaller, so-called daughter components. As the atom breaks apart, energy is released in the form of electromagnetic waves and electrically charged bits of matter. This energy is known as radiation (Radioactivity; Nuclear Energy).

Physical chemistry is fundamental to all chemistry and deals with the application of physical laws to chemical systems and chemical change. Much of physical chemistry is concerned with the role of energy in chemical reactions; this branch of physical chemistry is known as thermodynamics. Other major areas of study in physical chemistry are the rates and mechanisms of reactions, called chemical kinetics. A third area of physical chemistry studies molecular structure. Physical chemists study molecular structure by examining the spectrum of electromagnetic energy emitted by molecules and explain structure using principles of quantum mechanics.

Important subfields of physical chemistry include electrochemistry, which deals with the behavior of chemical substances subjected to electric current and the production of electrical energy by chemical systems. Other subfields of physical chemistry are colloid chemistry, which is concerned with the behavior of finely divided particles of matter; surface chemistry, which deals with the nature of surfaces and adsorption on them (see Photochemistry); and statistical mechanics, which applies the laws of probability to large numbers of particles.

Analytical chemistry is the science of separating complex materials into simpler ones and detecting and measuring the constituents. In a sense, analytical chemistry is the oldest branch of chemistry. A major feature of chemical analysis today is the wide use of physical instruments and computer control to automate the analysis of complex materials.

Biochemistry is the chemistry of living organisms and life processes. Even the simplest living thing is a complex chemical factory. Biochemists must have a detailed knowledge of organic chemistry. In some aspects of biochemistry, advanced physical chemistry is used, and biophysics and molecular biology are companion sciences.

Geochemistry is the application of chemistry (and, inevitably, physics) to processes taking place in the earth, such as mineral formation, the metamorphosis of rocks, and the formation and migration of petroleum.

Fields such as biochemistry, geochemistry, and materials science reveal the unity of the sciences. The divisions between chemistry, physics, biology, and geology are arbitrarily created for the convenience of humans—nature takes little account of these divisions.