In chemistry a compound is a type of substance consisting of molecules or molecular entities
that in turn are composed of two or more kinds of atoms linked together . Thus compound is
always a structure of atoms of more than one element held together by chemical bonds. By the
type of bonding chemical compounds are subdivided into four groups:
1. Molecular compounds whose molecules are formed of atoms held together by covalent
2. Ionic compounds whose atoms(ions) are linked together by ionic bonds.
3. Intermetallic compounds consisting of atoms of metals which are held together by
4. So called complexes that represent compounds whose molecules consist of atoms that
are held together by coordinate covalent bonds.
Every compound has a chemical formula that shows the types and proportions of atoms that
constitute a particular chemical compound.
Atoms of a certain chemical element bonded together is not a chemical compound because
only one type of atoms is involved. To form a compound we need to have atoms of at least two