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 $B _{2}=10$
$B _{2}=\sigma 1 s^{2} \sigma^{*} 1 s^{2} \sigma 2 s^{2} \sigma^{*} 2 s^{2} \pi 2 p_{y}^{1} \pi 2 p_{z}^{1}$
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.