Determine the bond angles in the following ions: (a) NH4^+ (b) SO3^2- ; (c) NO2^- ; (d) XeF5^+

Name: Problem 27, Chapter 9: Chemistry The Science in Context
Uploaded: 2020-05-01T19:45:46-08:00
Duration: 3 min 11 s
Channel: David Collins
Description: Determine the bond angles in the following ions: (a) NH4^+ (b) SO3^2- ; (c) NO2^- ; (d) XeF5^+

step 1 To determine the bond angles found in all of these molecules, we will first draw the Lewis struc

Determine the bond angles in the following ions: (a) NH4^+...

Key Concepts

Formal Charge Considerations

While the formal charge on atoms in an ion does not directly determine bond angles, it can affect the distribution of electron density around the central atom. Variations in electron density may lead to subtle adjustments in bond angles as the molecule or ion seeks a configuration that minimizes overall repulsion and stabilizes the structure.

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a fundamental concept used to predict the three-dimensional shapes of molecules and polyatomic ions. It is based on the idea that electron pairs around a central atom, whether they are bonding or nonbonding (lone pairs), repel each other and arrange themselves as far apart as possible. This arrangement minimizes repulsions and determines the ideal bond angles of the molecule or ion.

Electron Geometry vs. Molecular Geometry

Electron geometry considers the complete arrangement of all electron pairs (bonding and lone pairs) around a central atom, while molecular geometry focuses solely on the positions of the atoms (bonding pairs). The presence of nonbonding electron pairs can lead to deviations from the ideal bond angles predicted by the electron geometry, as lone pairs tend to repel more strongly than bonding pairs.

Lone Pair Repulsion Effect

Lone pairs of electrons have a stronger electron-electron repulsion compared to bonding pairs because they are localized closer to the central atom. This increased repulsion causes the bonding pairs to be pushed closer together, thereby reducing the bond angles relative to the idealized geometrical shapes. Understanding the impact of lone pairs is crucial in predicting the actual geometry of a molecule or ion.

Ion Geometry and Symmetry

The overall shape of a polyatomic ion, including its bond angles, is influenced by both the number of electron pairs around the central atom and how symmetrically these electron pairs are arranged. Highly symmetrical electron arrangements, such as tetrahedral or trigonal planar structures, typically have bond angles close to their ideal values, whereas asymmetrical distributions, often due to the presence of lone pairs, result in deviations from these ideal bond angles.

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