Question

Which of the following ions is the most stable in aqueous solution ?
`(At . No . Ti = 22, V = 23, Cr = 24, Mn = 25)`
A. `Cr^(3+)`
B. `V^(3+)`
C. `Ti^(3+)`
D. `Mn^(3+)`

Answer 1

Correct Answer - D
Stability of transition metal ions is directly proportional to the unpaired electrons. The exactly half-filled and completely filled d-orbitals are extra stable.
`Cr^(3+)(21) = 3d^(3), 4s^(0)` (3 unpaired electrons)
`V^(3+)(20)=3d^(2), 4s^(0)` (2 unpaired electrons)
`Ti^(3+)(19)=3d^(1), 4s^(0)` (1 unpaired electrons)
`Mn^(3+)(22)= 3d^(4), 4s^(0)` (4 unpaired electrons)
So, `Mn^(3+)` ion is most stable in aqueous solution.