molecule

Atoms linking by covalent bonds can give different structures :

1. Molecular structure
A group of atoms linking together to form a molecule (neutral particle), e.g. CO2­, C6H12O6, -(CH2CH2)n- etc.

2. Polyatomic structure
A group of atoms linking together to form a polyatomic ion (charged particle), e.g. NH4+, CO32-, etc.

3. Giant covalent structure
A huge of number of atoms are held together by a network of covalent bonds, e.g. diamond, graphite, SiO2, etc.