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Ch.9 - Molecular Geometry and Bonding Theories
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.9 - Molecular Geometry and Bonding TheoriesProblem 21a,c,d
Chapter 9, Problem 21a,c,d

How many nonbonding electron pairs are there in each of the following molecules: (a) (CH3)2S (c) BF3 (d) SO2

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Identify the central atom in the molecule, which is sulfur (S) in this case.
Determine the total number of valence electrons for the central atom. Sulfur has 6 valence electrons.
Count the number of bonds formed by the central atom. In (CH_3)_2S, sulfur forms two single bonds with two CH_3 groups.
Calculate the number of electrons used in bonding. Each single bond uses 2 electrons, so 2 bonds use 4 electrons.
Subtract the number of bonding electrons from the total valence electrons to find the number of nonbonding electrons. Divide this number by 2 to find the number of nonbonding pairs.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Valence Shell Electron Pair Repulsion (VSEPR) Theory

VSEPR theory is a model used to predict the geometry of individual molecules based on the repulsion between electron pairs in the valence shell of the central atom. According to this theory, electron pairs, whether bonding or nonbonding, will arrange themselves to minimize repulsion, which helps in determining the molecular shape and the presence of lone pairs.
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Valence Shell Electron Pair Repulsion Theory

Lone Pairs

Lone pairs are pairs of valence electrons that are not involved in bonding and are localized on a single atom. In molecular structures, these nonbonding electron pairs can influence the shape of the molecule and its reactivity, as they occupy space and can repel bonding pairs of electrons.
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Lone Pair Positions

Molecular Structure of (CH3)2S

The molecular structure of dimethyl sulfide, (CH3)2S, consists of a sulfur atom bonded to two methyl groups (CH3). The sulfur atom has two lone pairs of electrons, which are crucial for determining the overall shape of the molecule and its polarity. Understanding the arrangement of these atoms and electron pairs is essential for identifying the number of nonbonding electron pairs.
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Related Practice
Textbook Question

In which of the following molecules can you confidently predict the bond angles about the central atom, and for which would you be a bit uncertain? Explain in each case. (a) H2S, (b) BCl3, (c) CH3I, (d) CBr4, (e) TeBr4.

Textbook Question

Would you expect the nonbonding electron-pair domain in NCl3 to be greater or smaller in size than the corresponding one in PCl3?

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Textbook Question
How many electron domains are surrounding the central atoms which adopt the following geometries? (d) trigonal bipyramidal.
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Textbook Question

How many nonbonding electron pairs are there in each of the following molecules: (b) HCN

Textbook Question

How many nonbonding electron pairs are there in each of the following molecules: (b) HCN