Question

question 3 (1 point)
based on the vsepr theory, which one of the following molecules is linear?

bf₃
hcn
pcl₅
no₂⁻
so₂

Explanation:

• For \(BF_3\): Boron has 3 valence electrons. Each \(F\) atom contributes 1 electron for bonding. The central \(B\) atom has 3 bonding pairs and 0 lone pairs. According to VSEPR, it has a trigonal - planar geometry.
• For \(HCN\): Carbon has 4 valence electrons. It forms a single bond with \(H\) (1 electron from \(H\)) and a triple bond with \(N\) (3 electrons from \(N\)). The central \(C\) atom has 2 electron - group (1 single bond + 1 triple bond, which counts as 2 electron - groups around the central atom). So, it has a linear geometry.
• For \(PCl_5\): Phosphorus has 5 valence electrons. Each \(Cl\) atom contributes 1 electron for bonding. The central \(P\) atom has 5 bonding pairs and 0 lone pairs. According to VSEPR, it has a trigonal - bipyramidal geometry.
• For \(NO_2^-\): Nitrogen has 5 valence electrons. There is a negative charge (1 extra electron). Oxygen atoms contribute electrons for bonding. The central \(N\) atom has 3 electron - groups (2 bonding pairs and 1 lone pair). According to VSEPR, it has a bent geometry.
• For \(SO_2\): Sulfur has 6 valence electrons. Each \(O\) atom contributes electrons for bonding. The central \(S\) atom has 3 electron - groups (2 bonding pairs and 1 lone pair). According to VSEPR, it has a bent geometry.

Answer:

HCN