State the atomicity of neon.

'A radical takes part - unsplit in a chemical reaction 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.

Explain the term -'valency'. State giving reasons the valency of -

a] Chlorine in hydrogen chloride b] Sulphate in sulphuric acid

c] Nitrogen in ammonia d] Magnesium in magnesium oxide.