Question

question 2 (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 fluorine atom contributes 1 electron for bonding. So, \(BF_3\) has 3 bonding pairs and no lone pairs around the central boron atom. According to VSEPR theory, it has a trigonal - planar geometry (\(sp^2\) hybridization).
• For \(HCN\):
• Carbon has 4 valence electrons. It forms a single bond with hydrogen (using 1 electron) and a triple bond with nitrogen (using 3 electrons). So, there are 2 electron - group (one single bond and one triple bond, which are considered as two regions of electron density) around the central carbon atom. It has a linear geometry (\(sp\) hybridization).
• For \(PCl_5\):
• Phosphorus has 5 valence electrons. Each chlorine atom contributes 1 electron for bonding. So, \(PCl_5\) has 5 bonding pairs and no lone pairs around the central phosphorus atom. According to VSEPR theory, it has a trigonal - bipyramidal geometry (\(sp^3d\) hybridization).
• For \(NO_2^-\):
• Nitrogen has 5 valence electrons. After accounting for the negative charge (1 extra electron), and bonding with two oxygen atoms. There are 3 electron - groups (2 bonding pairs and 1 lone pair) around the central nitrogen atom. According to VSEPR theory, it has a bent geometry (\(sp^2\) hybridization).
• For \(SO_2\):
• Sulfur has 6 valence electrons. After bonding with two oxygen atoms, there are 3 electron - groups (2 bonding pairs and 1 lone pair) around the central sulfur atom. According to VSEPR theory, it has a bent geometry (\(sp^2\) hybridization).

Answer:

B. \(HCN\)