The d-electron configuration of Cr3+, Mn2+, Fe2+ and Ni2+ are 3d4, 3d5, 3d6 and 3d8 respectively. Which one of the following aqua complexes will exhibit the minimum paramagnetic behaviour?
(At. no. Cr = 24, Mn = 25, Fe = 26, Ni = 28)
[Mn(H2O)6]2+
[Fe(H2O)6]2+
[Ni(H2O)6]2+
[Ni(H2O)6]2+
A.
[Mn(H2O)6]2+
As the number of unpaired electron increases, the magnetic moment increases and hence the paramagnetic behaviour increases.
so, Cr2+ (22) = 3d4 - 4 unpaired electrons
Mn2+ (23) = 3d5 - 5 unpaired electrons
Fe2+ (24) = 3d6 - 4 unpaired electrons
Ni2+ (26) = 3d8 -2 unpaired electrons
So, [Ni(H2O)6]2+ exhibit minimum paramagnetic behaviour.
