Question

which of the lewis structures in the image is correct?

Explanation:

Step1: Analyze option A

For \( PCl_3 \), phosphorus has 5 valence electrons. Each chlorine has 7 valence electrons. In \( PCl_3 \), P forms 3 single bonds with Cl (using 3 of its valence electrons), and has one lone pair. Each Cl has 3 lone pairs. The Lewis structure in option A correctly represents these bonding and non - bonding electrons.

Step2: Analyze option B

For \( SO_2 \), sulfur has 6 valence electrons. In \( SO_2 \), sulfur should have a double bond with one oxygen and a single bond with another (or two double bonds in a resonance structure), and also a lone pair. The structure in option B does not account for the correct bonding (sulfur should have more than two bonds or a different bond - type distribution considering its valence electrons and the octet rule for surrounding atoms).

Step3: Analyze option C

For \( HCN \), carbon should form a triple bond with nitrogen (C has 4 valence electrons, N has 5 valence electrons). In \( HCN \), \( H - C\equiv N \), but the structure in option C shows \( H - C = N \) which is incorrect as it does not satisfy the octet rule for carbon and nitrogen (carbon would have only 4 electrons from bonds in this incorrect structure, and nitrogen would have 6 instead of 8).

Step4: Analyze option D

For \( CBr_2 \), carbon has 4 valence electrons. Each bromine has 7 valence electrons. Carbon should form two single bonds with bromine (using 2 of its valence electrons) and have two lone pairs. Each bromine should have 3 lone pairs. The structure in option D does not show the lone pair on carbon, so it is incorrect.

Answer:

A. Option A's Lewis structure is correct.