Question

The molecule/ion having diamagnetic nature and a bond order of $1.0$ is

• A. $H{e}_2^{+}$
• B. $L{i}_2^{+}$
• C. $B_2$
• D. None

Answer 1

Answer: (A)

$H{e}_2^{+}=\sigma 1s^2<{\sigma }^{\ast }1s^1$

$BO=\frac{2-1}{2}=0.5$

$H{e}_2^{+}$ ion having one unpaired electron. So, it is paramagnetic.

$L{i}_2^{+}=\sigma 1s^2<{\sigma }^{\ast }1s^2<\sigma 2s^1$

$BO=\frac{3-2}{2}=0.5$ (Paramagnetic)

$B_2=\sigma 1s^2<{\sigma }^{\ast }1s^2<\sigma 2s^2<{\sigma }^{\ast }2s^2<\pi 2p_x^1=\pi 2p_y^l$

$BO=\frac{6-4}{2}=1$ (Paramagnetic)

$C_2\to \sigma 1s^2{<}^{\ast }\sigma 1s^2<\sigma 2s^2<\ast \sigma 2s^2<\pi 2p_x^2=\pi 2p_y^2$

$BO=\frac{8-4}{2}=2$ (Diamagnetic)