Question

Octet rule is not valid for which of the following molecules?

• A. $C{O}_2$
• B. $B{H}_3$
• C. $N_2$
• D. $O_2$

Answer 1

The correct option is B $B{H}_3$

(a) Carbon and oxygen have 8 electrons in their valence shell and thus obey the octet rule.

(b) Boron atom does not satisfy the octet rule after bonding with hydrogen as it contains only 6 valence electrons in the outermost shell.


(c) $N$ have 5 valence electrons, three of them is shared with the other N atom forming a triple bond and thus also satisfies octet.
(d) Both the oxygen atoms are satisfying the octet rule.
Hence, the octet rule is not valid for $B{H}_3$.