Atoms of the same element or different elements combine to form a molecule. Give two examples each of –

(a) atoms of the same element

(b) atoms of different elements combining to form a molecule.

Explain the term – 'atomicity'. Give a reason why –

(a) Helium is considered monoatomic, but hydrogen a diatomic molecule.

(b) Ozone is considered triatomic, but phosphorus a tetratomic molecule.

'A radical takes part — unsplit in a chemical reaction and retains its identity in reactions'. With reference to the radical:

(a) ammonium

(b) bisulphate

(c) carbonate — state the group of atoms present in each radical.

Differentiate between the following with suitable examples — A basic radical and a acid radical.