Question

The bond order and magnetic characteristics of CN^- are :-

• A. 3, Paramagnetic
• B. 2.5, Diamagnetic
• C. 3, Diamagnetic
• D. 2.5, Paramagnetic

Answer 1

The correct option is C

3, Diamagnetic

The correct answer is option C.

Explanation of correct answer:-

Step 1:- Electronic configuration of CN^- using MOT

The bond order and magnetism can be calculated from MOT(Molecular Orbital Theory).

CN^- is a 14 electron system out of which 10 are bonding and 4 are anti-bonding electrons, therefore, the MOT electronic configuration of CN^- is written as $\left(\mathrm{\sigma }1{\mathrm{s}}^2\right)\left({\sigma }^{*}1s^2\right)\left(\sigma 2s^2\right)\left({\sigma }^{*}2s^2\right)\left(\pi 2p_x^2\right)\left(\pi 2p_y^2\right)\left(\pi 2p_z^2\right)$

Step 2:- Calculation of Bond order by using the formula given below:
$\mathrm{Bond}\mathrm{order}=\frac{1}{2}\left({\mathrm{N}}_{\mathrm{b}}-{\mathrm{N}}_{\mathrm{a}}\right)$

where, N_b = no. of bonding electrons = 10

N_a = no. of anti-bonding electrons = 4

$$\begin{gathered} \mathrm{Bond}\mathrm{order}=\frac{1}{2}\left(10-4\right) \\ =\frac{6}{2} \\ =3 \end{gathered}$$

Final answer:- Bond order of CN^- is 3, It is Diamagnetic in nature, since it does not have any unpaired electrons.