Question

Paramagnetism is directly related with presence of unpaired electron. As each unpaired electron has a magnetic moment associated with its spin angular momentum and orbital angular momentum.
For the $3d$ series, the contribution of orbital angular momentum is effectively quenched and hence is of considerably importance. Thus, the magnetic moment is determined by the number of unpaired electrons and is calculated by using the spin only formula, i.e.
$\mu =\sqrt{n(n+2)}BM$
where $h_n=$ number of unpaired electrons.
Magnetic moment of a transition metal ion is found to be $3.87BM$. The number of unpaired electrons present in it is

• A. 2
• B. 3
• C. 4
• D. 5

Answer 1

Answer: (B)

$\because \mu =\sqrt{n(n+2)}$
$\therefore 3.87=\sqrt{n(n+2)}$
On solving, $n=3$