Question

Exception of octet rule is:

• A. $K$
• B. $Ca$
• C. $N$
• D. $He$

Answer 1

The correct option is D $He$

For Helium, there is no $1p$ level according to the quantum theory so that $1s$ is a closed shell having two electrons and no p level. So atoms before and immediate after $He$ follow a duet rule.

Thus, the exception of the octet rule is He.

Hence, the correct option is $\text{D}$