Glossary of geography

Chemistry

Chemistry (pronounced: kem-is-tree, from the Greek word khēmeía meaning "cast together") is the scientific discipline involved with elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.

Atom

An atom (pronounced: a-tom, from the Greek word atomos meaning "indivisible") is the smallest unit of a chemical element that retains the properties of that element.

Related terms: Molecule, Ion, Element, Compound

Molecule

A molecule (pronounced: mol-e-cule, from the Latin word molecula meaning "small mass") is the smallest particle in a chemical element or compound that has the chemical properties of that element or compound.

Related terms: Atom, Ion, Element, Compound

Ion

An ion (pronounced: i-on, from the Greek word iōn meaning "going") is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Related terms: Atom, Molecule, Element, Compound

Element

An element (pronounced: el-e-ment, from the Latin word elementum meaning "principle") is a substance whose atoms all have the same number of protons - i.e. the same atomic number.

Related terms: Atom, Molecule, Ion, Compound

Compound

A compound (pronounced: com-pound, from the Latin word componere meaning "put together") is a substance formed when two or more chemical elements are chemically bonded together.

Related terms: Atom, Molecule, Ion, Element