Question

How to find charge or valency of a radical like Sulphate or Nitrate?

Answer 1

SO4 has a valency of 2 . To find its valency ,I can advice you 2 ways which I often use are:

a•SO4 is an anion which has came from an acid H2SO4, in which hydrogen as always has valency 1. Since hydrogen is more electro+ve than SO4,its oxidation no. will be +1. So by using this information we can find oxidation no. of SO4.

Let x be oxidation no. of SO4. Since, the sum of oxidation nos. will be zero, so equating it with zero:

2×H+1×SO4=0

2×1+1×x=0

x=-2Which is the oxidation no. of SO4.

This implies that it has valency 2.

Note: Remember Valency is combining capacity ,it does not have +or - charge, while oxidation no. show whether it can gain(+ve charge) or lose (-ve charge) electrons.

b• Sulphur has 6 electrons in its Valence shell& oxygen has a oxidation no. -2 so when 4 oxygens combine with 1 Sulphur , the octet of the Sulphur is extended by by 2 more electrons(Sulphur has 6 electrons & 4Oxygens gives it 8 electrons i.e., 2 more electrons) which gives SO4 a oxidation no. Of -2 & valency 2.