Question

The hexaquo manganese(II) ion contains five unpaired electrons, while the hexacyanoion contains only one unpaired electron. Explain using the crystal field theory.

Answer 1

Mn is `+2` state the configuration `3d^(5)`. In presence of `H_2O` as ligand, the distribution of these five electrons is `t_(2g)^(3)e_(g)^(2)`, i.e., all the electrons remain unpaired. In presence of `CN^(ɵ)` as ligand, the distribution is `t_(2g)^(5)e_(g)^(0)`, i.e., two `t_(2g)` orbitals contain paired electrons while the third `t_(2g)` orbital contains one unpaired electron.