Question

Which of the following has maximum number or unpaired electrons?

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

Answer 1

Answer: (C)

(i) $Cu ^{+}(Z=29) [ Ar ] 3 d^{10} 4 s^{0}$
It has no unpaired electron.
(ii) $Zn (Z=30) [Ar] 3 d^{10} 4 s^{2}$
It has no unpaired electron.
(iii) $Fe ^{2+}(Z=26) [ Ar ] 3 d^{6} 4 s^{0}$
It has four unpaired electrons.
(iv) $Ni ^{3+}(Z=28):[ Ar ] 3 d^{7} 4 s^{0}$
It has three unpaired electrons
Therefore $Fe ^{2+}$ has maximum number of unpaired electrons
A paramagnetic species has unpaired electrons. A diamagnetic species has no unpaired electrons.