The magnetic moment of $\mathrm{Ni}^{2+}$ ion (atomic number of $\mathrm{Ni}=28$ ) in BM unit is

• A

  1.73
• B

  4.81
• C

  5.96
• Correct answer
  D

  2.84

Solution

$\mathrm{Ni}_{28}=[\mathrm{Ar}]_{18} 3 \mathrm{~d}^8 4 \mathrm{~s}^2, \mathrm{Ni}^{2+}=[\mathrm{Ar}]_{18} 3 \mathrm{~d}^8 4 \mathrm{~s}^2$ Number of unpaired electrons $=2$ Magnetic moment, $\mu=\sqrt{n(n+2)}=\sqrt{2(2+2)}=\sqrt{8}=2.84 \mathrm{BM}$

Hence, the correct answer is option: 'D'.