Solution :
A complex ion may be defined as a metal ion that is located at the center with other molecules or ions surrounding the center ion.
In the context, the number of the unpaired electrons for the following complex ions are :
1. [tex]$Ru(NH_3)62+$[/tex] (low spin)
[tex]$Ru^{2+} = [Kr] \ 4d^6 \ 5s^0$[/tex]
Here all the d-electrons are paired. Therefore, there are no unpaired electrons.
2. [tex]$Ni(H_2O)62+$[/tex] (high spin)
[tex]$Ni^{2+} = [Ar] \ 4s^0 \ 3d^8$[/tex]
Therefore, it has two unpaired electrons.
3. [tex]$V(en)33+$[/tex] (high spin)
[tex]$V=[Ar] \ 3d^2 \ 4s^0$[/tex]
It has 2 unpaired electrons
