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

Options

A. `[Mn(H_(2)O)_(6)]^(3+)`
B. `[Fe(H_(2)O)_(6)]^(3+)`
C. `[Co(H_(2)O)_(6)]^(2+)`
D. `[Co(H_(2)O)_(6)]^(3+)`

Answer

B

Explanation

The CFSE for octahedral complex is given by
`=[-0.4 t_(2g)e^(-)+6.0 e _g e ^-]`
For `Mn^(3+),[3d^4]rarrt_(2g)^3e_(g)^1`
`therefore CFSE = [ (-0.4 xx 3 )+(0.6 xx1)]=-0.6`
For `Fe^(3+),[3d^5]rarrt_(2g)^3e_(g)^2`
` CFSE = [ (-0.4 xx 3 )+(0.6 xx2)]= 0`
For `Co^(2+),[3d^7]rarrt_(5g)^3e_(g)^2`
` CFSE = [ (-0.4 xx 5 )+(2 xx0.6)]=-0.8`
For `Co^(3+),[3d^6]rarrt_(4g)^3e_(g)^2`
` CFSE = [ (-0.4 xx 4 )+(2 xx0.6)]=-0.4`