Question

Assertion : $B_2$ molecule is diamagnetic.
Reason : The highest occupied molecular orbital is of $\sigma$ type.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (D)

The total number of electrons in $B_2=10$
$B_2=\sigma 1s^2{\sigma }^{\ast }1s^2\sigma 2s^2{\sigma }^{\ast }2s^2\pi 2p_y^1\pi 2p_z^1$
It has two unpaired electrons
$\therefore$ It is paramagnetic and the highest occupied molecular orbital is of $\pi$ type. Thus, both assertion and reason are false.