Which of the following complex ions has electrons that are symmetrically filled in both `t_(2g) and e_(g)` orbitals ?

Options

A. `[FeF_(3)]^(3-)`
B. `[mn(CN)_(6)]^(4-)`
C. `[CoF_(6)]^(3-)`
D. `[Co(NH_(3))_(6)]^(2+)`

Answer

A

Explanation

In presence of week field ligand in an octahedral complex, electrons of metal ion could not paired up and produce symmetrical field in case of `d^(5)` configuration . While in presence of strong field ligands electrons of metal ion paired ion paired up and produce unsymmetrical field in case of `d^(4), d^(5), d^(6) and d^(7).`
`[Fe F_(3) ]^(3-) ,` oxidation state of ` Fe =+3`
` So ,Fe ^(3+)=[Ar]3d^(5) ` where `F^(-)` is a weak field ligand
Hence `[FeF_(3 )]^(3-)` produces more symmetrical field
`i.e., t_(2g)^(3)e_(g)^(2)`

`[Mn(CN)_(6)]^(4-)` oxidation state of `Mn =+2`
`SO Mn^(2+)=[Ar3d^(5) ` where ` CN^(-)` si strong field ligand So it produce unsymmetrical field
`i.e.,t_(2g)^(5)e_(g)^(0)`

`[CoF_(6)]^(3-)`,oxidation state of `Co=+3`
`"so " Co^(3+)=[Ar]3d^(6)`
Due to weak field ligand of `F^(-) ` , it produces unsymmetrical field `i.e., t_(2g)^(4)e_(g) ^(2)`

`[Co(NH_(3))_(6)]^(2+),` oxidation state of `Co =+2`
`So " " CO^(2+)=[Ar]3d^(7)`
where `NH_(3)` is weak field ligand , so it produce unsymmetrical field `t_(2g)^(5)e_(g)^(2)`