Question

The octet rule is not valid for the molecule

• A. ${\mathrm{H}}_2\mathrm{O}$
• B. ${\mathrm{O}}_2$
• C. $\mathrm{NO}$
• D. ${\mathrm{CO}}_2$

Answer 1

The correct option is C

$\mathrm{NO}$

Explanation for correct option

(C)$\mathrm{NO}$

Octet rule

• "According to this, atoms can combine either by transfer of valence electrons from one atom to another (gaining or losing) or by sharing valence electrons in order to have an octet in their valence shells. "
• This is known as the octet rule.

Limitation of the octet rule

• The octet rule is not satisfied for all atoms in compounds with an odd number of electrons, such as nitric oxide$\left(\mathrm{NO}\right)$ and nitrogen dioxide$\left({\mathrm{NO}}_2\right)$.
• So, the octet rule is not valid for the molecule $\mathrm{NO}$.

Explanation for incorrect option

• The octet rule is valid for ${\mathrm{H}}_2\mathrm{O}$.
• 
• The octet rule is valid for ${\mathrm{O}}_2$.
• 
• The octet rule is valid for ${\mathrm{CO}}_2$
• 
• Hence, options(A), (B),and (D) are incorrect.

So, option (C) is correct. The octet rule is not valid for the molecule $\mathrm{NO}$.