Among the following complexes, the one which shows zero crystal field stabilization energy (CFSE) is

Options

A. (a) `[Mn(H_2O)_6]^(3+)`
B. (b) `[Fe(H_2O)_6]^(3+)`
C. (c) `[Co(H_2O)_6]^(2+)`
D. (d) `[Co(H_2O)_6]^(3+)`

Answer

B

Explanation

`H_2O` is a weak ligand
`CFSE=(-0.4x+0.6y)Delta_0`
where x and y are electrons present in `t_(2g)` and `e_g` orbitals.
For `[Fe(H_2O)_6]^(3+)` complex ion
`Fe^(3+)(3d^5)=t_(2g)^3e_g^2=-0.4xx3+0.6xx2=0`