IIT-JEE 2010 · Paper 2 · Chemistry Q6

ChemistrySingle correct+5 / -2Question 6 of 57

Assuming that Hund's rule is violated, the bond order and magnetic nature of the diatomic molecule $\ce{B2}$ is

1 and diamagnetic

0 and diamagnetic

1 and paramagnetic

0 and paramagnetic

Answer and worked solution

Official answer: A

$\ce{B2}$ has 10 electrons: $\sigma1s^2\sigma^*1s^2\sigma2s^2\sigma^*2s^2$ and then two electrons in the degenerate $\pi2p_x,\pi2p_y$ pair.

Hund's rule violated. Both electrons go into the same π orbital with opposite spins: no unpaired electrons, diamagnetic.

Bond order is unchanged: $\frac{6-4}2=1$ .

(A)

Topics:Molecular orbital theory

IIT-JEE 2010 · Paper 2, Chemistry question 6