The d-electron configurations of `Cr^(2+), Mn^(2+), Fe^(2+)` and `Co^(2+)` are `d^4,d^5,d^6` and `d^7` respectively. Which one of the following will exhibit minimum paramagnetic behaviour ? (At. nos. Cr = 24, Mn = 25, Fe = 26, Co = 27)

Options

A. `[Cr(H_2O)_6]^(2+) and [CoCl_4]^(2)`
B. `[Cr(H_2O)_6]^(2+) and [Fe(H_2O)_6]^(2+)`
C. `[Mn(H_2O)_6]^(2-) and [Cr(H_2O)_6]^(2+)`
D. `[CoCl_4]^(2+) and [Fe(H_2O)_6]^(2+)`

Answer

B

Explanation

`[Cr(H_2O)_6]^(2+)` has `4s^0 3d^4` electronic configuration, has four unpaired electrons. `[Fe(H_2O)_6]^(2+)` has `4s^0 3d^6` has four unpaired electrons.