Which of the following ions is the most stable in aqueous solution ?
`(At . No . Ti = 22, V = 23, Cr = 24, Mn = 25)`

Options

A. `Mn^(2+)`
B. ` Cr^(3+)`
C. `V^(3+)`
D. `Ti^(3+)`

Explanation

Out of the given species, `Cr^(3+)` has the highest negative reduction potential.Hence, it cannot be reduced to `Cr^(2+)` and, therefore, is the most stable ion in aqueous solution.
Alternatively,
`Mn^(3+) = [ AAr] 3d^(4) , Cr^(3+)= [Ar]3d^(3)`
`V^(3+) =[Ar]3d^(2)Ti ^(3+) = [ Ar] 3d^(1)`
In `Cr^(3+)`, all three d electrons enter into lower energy `t_(2g)` orbitals. The lowering of energy is maximum and hence stability is maximum.