A chemical compound is a chemical substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound.
There are four types of compounds, depending on how the constituent atoms are held together:
molecules held together by covalent bonds
ionic compounds held together by ionic bonds
intermetallic compounds held together by metallic bonds
certain complexes held together by coordinate covalent bonds.