- An atom is the smallest particle of an element that can be further decomposed into subatomic particles. These subatomic particles are electron, proton and neutron. Example of atoms are Hydrogen (H), Carbon (C), Sulphur (S) and Iron (Fe).
- Atoms of an element take part into chemical reactions without further decomposition into subatomic particles.
- An Atom of an element can not be free state.
- Atoms can loose and gain electrons to form ions. If an atom Looses electronic then it becomes positive ion. And if it gains electron then it becomes negative ion.
- Mass of an atom cannot be determined practically.
- A molecule is formed by combining two or more atoms of same element or different elements. Examples of molecule are O2, N2, O3 and NaCl etc.
- Generally molecules do not take part in chemical reactions.
- Molecules can live in free state.
- Molecules can not loose or gain electrons to form ions.
- The sum of masses of individual atoms constitute the mass of a molecule.