Multiple Choice
According to Valence Shell Electron Pair Repulsion (VSEPR) Theory, why do lone (nonbonding) pairs of electrons on a central atom affect the molecular shape?
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12. Molecular Shapes & Valence Bond Theory
Valence Shell Electron Pair Repulsion Theory
Multiple Choice
Which of the following molecules has the greatest number of electron groups around its central atom?
A
CH4
B
PCl5
C
SF6
D
NH3
Verified step by step guidance1
Identify the central atom in each molecule: for CH4 it's C, for PCl5 it's P, for SF6 it's S, and for NH3 it's N.
Recall that the number of electron groups around the central atom includes both bonding pairs (single, double, or triple bonds count as one group each) and lone pairs of electrons on the central atom.
Determine the number of bonding groups for each molecule: CH4 has 4 bonds, PCl5 has 5 bonds, SF6 has 6 bonds, and NH3 has 3 bonds.
Check for lone pairs on the central atom: CH4 has 0 lone pairs, PCl5 has 0 lone pairs, SF6 has 0 lone pairs, and NH3 has 1 lone pair.
Add the bonding groups and lone pairs for each molecule to find the total number of electron groups around the central atom, then compare these totals to identify which molecule has the greatest number.
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