The d electron congfiguration of `Cr^(2+)` , `Mn^(2+)` , `Fe^(2+)` and `Ni^(2+)` are `3d^(4)` , `3d^(5)` , `3d^(6)` and `3d^(8)` respectively. Which one of the folowing aqua complexes will exhibit the minimum paramagnetic behaviour ?
`(At. No . Cr = 24, Mn = 25, Fe = 26, Ni = 28)`

Options

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

Answer

B

Explanation

As the number of unpaired electron increases, the magnetic moment increases and hence, the paramagnetic behaviour increases.
`So, Cr^(2+)(22)=3d^(4)" (4 unpaired electrons)"`
`Mn^(2+)(23)=3d^(5)" (5 unpaired electrons)"`
`Fe^(2+)(24)=3d^(6)" (4 unpaired electrons)"`
`Ni^(2+)(26)=3d^(8)" (2 unpaired electrons)"`
`So, [Ni(H_(2)I)_(6)]^(2+)" exhibit minimum paramagnetic behaviour"`