Question

Which of the following has maximum number of unpaired $d$-electrons?

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

Answer 1

Answer: (A)

$Fe ^{2+}=[ Ar ] 3 d^{6} 4 s^{0}$
$\Rightarrow 4$ unpaired electrons.
$Cu ^{+}=[ Ar ] 3 d^{10} 4 s^{0}$
$\Rightarrow $ No unpaired electron
$Zn =[ Ar ] 3 d^{10} 4 s^{2}$
$\Rightarrow $ No unpaired electron
$Ni ^{3+}=[ Ar ] 3 d^{7} 4 s^{0}$
$\Rightarrow 3$-unpaired electrons