Question
Are the oxidation state and covalency of Al in 
same?
Solution
Valency of chlorine = (-1)
Valency of water = 0
Let the oxidation state of Al be x.
x -1 0
[Al Cl (H2O)6]2+
x - 1 + 6(0) = +2
or x = +3
Thus the oxidation state of Al is +3. Since six legends (which can denote a pair of electrons) i.e. H2O molecules are attached to the alumninum atom, thereofre, its covalency is 6.
