Question

Assuming $2s-2p$ mixing is NOT operative, the paramagnetic species among the following is

• A. $B{e}_2$
• B. $B_2$
• C. $C_2$
• D. $N_2$

Answer 1

Answer: (C)

as it has two unpaired electrons
$B{e}_2=\sigma 1s^2{\sigma }^{\ast }1s^2,\sigma 2s^2{\sigma }^{\ast }2s^2$
$B_2=\sigma 1s^2{\sigma }^{\ast }1s^2,\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p_z^2$
$C_2=\sigma 1s^2{\sigma }^{\ast }1s^2,\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p_z^2\pi 2p_x^1\pi 2p_y^1$
$N_2=\sigma 1s^2{\sigma }^{\ast }1s^2,\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p_z^2\pi 2p_x^2\pi 2p_y^2$