CHEMISTRY

Chemistry , the science that deals with the
properties, composition, and structure of
substances (defined as elements and
compounds), the transformations they
undergo, and the energy that is released or
absorbed during these processes. Every
substance, whether naturally occurring or
artificially produced, consists of one or
more of the hundred-odd species of atoms
that have been identified as elements.
Although these atoms, in turn, are
composed of more elementary particles,
they are the basic building blocks of
chemical substances; there is no quantity
of oxygen, mercury, or gold, for example,
smaller than an atom of that substance.
Chemistry, therefore, is concerned not with
the subatomic domain but with the
properties of atoms and the laws governing
their combinations and how the knowledge
of these properties can be used to achieve
specific purposes.