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.

Give the symbol and valency of the following elements & radicals.
a] Potassium
b] Sodium
c] Hydrogen
d] Calcium
e] Aluminium
f] Magnesium
g] Zinc
h] Chlorine [chloride]
i] Sulphur [sulphide]
j] Nitrogen [nitride]
k] Oxygen [oxide]
l] Ammonium
m] Bicarbonate
n] Nitrate
o] Bisulphate

p] Bisulphite
q] Hydroxide
r] Carbonate
s] Sulphate
t] Sulphite