Question

The correct order of number of unpaired electrons is

• A. $Cu^{2 +} > Ni^{2 +} > Cr^{3 +} > Fe^{3 +}$
• B. $Ni^{2 +} > Cu^{2 +} > Fe^{3 +} > Cr^{3 +}$
• C. $Fe^{3 +} > Cr^{3 +} > Ni^{2 +} > Cu^{2 +}$
• D. $Cr^{3 +} > Fe^{3 +} > Ni^{2 +} > Cu^{2 +}$

Answer 1

Answer: (C)

$Fe^{3 +} > Cr^{3 +} > Ni^{2 +} > Cu^{2 +}$

Answer 2

$Fe^{3 +} - 3d^{5}$ No. of unpaired electrons = 5

$Cr^{3 +} - 3d^{3}$ No. of unpaired electrons = 3

$Ni^{2 +} - 3d^{8}$ No. of unpaired electrons = 2

$Cu^{2 +} - 3d^{9}$ No. of unpaired electrons = 1