Question

based on the vsepr theory, which one of the following molecules is linear?
bf₃
hcn
pcl₅
no₂
so₂

Explanation:

VSEPR theory predicts molecular shape based on electron domains. A linear shape requires 2 electron domains (bonding pairs, no lone pairs on central atom).

• $\text{BF}_3$: Trigonal planar (3 bonding domains).
• $\text{HCN}$: Linear (C has 2 bonding domains: single bond to H, triple bond to N; no lone pairs).
• $\text{PCl}_5$: Trigonal bipyramidal (5 bonding domains).
• $\text{NO}_2^-$: Bent (2 bonding + 1 lone pair on N).
• $\text{SO}_2$: Bent (2 bonding + 1 lone pair on S).

Answer:

B. HCN