We have to calculate the valency f magnesium and chlorine in magnesium chloride.
Magnesium Chloride is a compound inorganic consisting of one magnesium and two chloride ions.
The electronic configuration of magnesium is [Ne]3s2 or can also be written as 2,8,2. This shows magnesium has 2 valence electrons in its outermost shell. If the valence electron is less than 4, it is recognised as valency.
As magnesium has 2 valence electron, its valency is 2.
The electronic configuration of chlorine is [Ne]3s2 3p5or can also be written as 2,8,7. This shows chlorine has 7 valence electrons in its outermost shell. If the valence electron is more than 4, then the valency can be calculated as follows:
Valency = Valence electron -8
Accordingly, the valency of chlorine is 7-8 which is -1.
Thus the valency of Mg is 2, whereas for chlorine it is -1 in MgCl2.