Question

The magnetic moment (spin only) of \[{[NiC{l_4}]^{2 - }}\] is:
A. 1.82 BM
B. 5.46 BM
C. 2.82 BM
D. 1.41 BM

Answer 1

Hint: The magnetic moment of a complex is calculated by the application of the formula of magnetic moment. But, before that, we have to find out two major things. First, whether the central metal has any unpaired electron or not and second whether the surrounding ligands are weak field or strong field ligands.

Complete step by step answer:
In order to calculate the magnetic moment in the given complex, we need to find out the oxidation state of the central metal atom, i.e. Nickel and then count the number of unpaired electrons in it.
As Ni atom is surrounded by 4 Cl- ions and the overall charge of the coordination complex is -2, the O.S of Ni will be:
$ x - 4 = - 2 \\
  x = + 2 \\
$
Hence, the oxidation state of Ni is +2.
The electronic configuration of Ni is= $[Ar]4{s^2}3{d^8}$
The electronic configuration of $Ni^2+$ is= $[Ar]4{s^0}3{d^8}$
As there are 8 electrons in the 3d-subshell, the number of unpaired electrons will be 2.

↑↓

↑↓

↑↓

↑

↑

      3d-subshell
 Now, we have to apply the formula for finding the magnetic moment of Ni2+ ion according to which,
Magnetic moment = $\sqrt {n(n + 2)} $ BM
Where, n = Number of unpaired electrons.
Thus, Magnetic moment = $\sqrt {2(2 + 2)} $ BM = 2.82 BM
Hence, the correct option is C i.e 2.82 BM.

Note:
The greater the number of unpaired electrons in the central metal atom of a coordination complex, the greater the value of magnetic moment and the greater the interaction of the complex with the external magnetic field. The unit of magnetic moment is Bohr Magneton.