Question 1
Multiple choiceMedium1 markFor molecules whose central atoms have four electron domains, the graph shows mean bond angle against the number of lone pairs on the central atom.
What is the average decrease in mean bond angle per added lone pair from 0 to 2 lone pairs, and the molecular geometry at 2 lone pairs?
Show answer and explanation
Answer: A. The average decrease is (109.5° − 104.5°) / (2 − 0) = 2.5° per added lone pair. With four electron domains and two lone pairs, the molecular geometry is bent.
B: subtracts the endpoint angles but does not divide by the two added lone pairs, giving 5.0° per lone pair.
C: assigns the trigonal-pyramidal geometry associated with one lone pair rather than the bent geometry for two.
D: combines the undivided angle change with the one-lone-pair geometry.
Remember: molecular geometry describes the arrangement of atoms, not lone pairs.