Question

Which of the following molecules does not obey octet rule?

• A. $CO_2$
• B. $CHCl_3$
• C. $ClF_3$
• D. $NH_3$

Hint:

Elements in Period 3 and below can expand their octet due to the availability of empty $d$-orbitals.

Answer 1

The Correct Option is C

Step 1: Concept
The octet rule states that atoms gain, lose, or share electrons to have eight electrons in their valence shell.

Step 2: Analysis
- $CO_2, CHCl_3,$ and $NH_3$ all have central atoms surrounded by 8 valence electrons. - In $ClF_3$, Chlorine has 7 valence electrons and forms 3 bonds with Fluorine, plus it retains 2 lone pairs. Total electrons = $3 (\text{bonds}) \times 2 + 2 (\text{lone pairs}) \times 2 = 10$ electrons.

Step 3: Conclusion
$ClF_3$ is an expanded octet molecule and does not obey the rule.
Final Answer: (C)