Calculate the number of unpaired electrons in the following gaseous ions :
`Mn^(3+),Cr^(3+),V^(3+)` and `Ti^(3+)`
Which one of these is the most stable in aqueous solution ?

Explanation

`Mn^(3+):3d^(4)` has 4 unpaired electrons, `Cr^(3+):3d^(3)` has 3 unpaired electrons, `V^(3+):3d^(2)` has 2 unpaired electrons, `Ti^(3+):3d^(1)` has 1 unpaired electron. `Cr^(3+)` is most stable out of these in aqueous solution because it has half-filled `t_(2g)` level (i.e., `t_(2g)^(3)`).