Problem 51 - Chemistry: The Central Science in SI Units, Global Edition

Question

Indicate the hybridization of the central atom in (a) \(\mathrm{H}_{2} \mathrm{~S}\), (d) \(\mathrm{AlI}_{3}\). (b) \(\mathrm{SeF}_{6},(\mathbf{c}) \mathrm{P}(\mathrm{OH})_{3}\)

Step-by-Step Solution

Answer

The hybridization of the central atoms for each molecule is: a) \(H_2S\): sp^3 b) \(SeF_6\): sp^3d^2 c) \(P(OH)_3\): sp^2 d) \(AlI_3\): sp^2

Step 1: Determine the electron domains for each molecule

First, we need to identify the central atom and electron domains for each molecule mentioned above to estimate the geometry of these molecules. We can do this by counting the number of lone electron pairs and the number of covalent bonding groups around the central atom. For molecule (a) \(H_2S\): Central atom: S Lone pair of electrons: 2 Number of bonded atoms: 2 For molecule (b) \(SeF_6\): Central atom: Se Lone pair of electrons: 0 Number of bonded atoms: 6 For molecule (c) \(P(OH)_3\): Central atom: P Lone pair of electrons: 0 Number of bonded atoms: 3 For molecule (d) \(AlI_3\): Central atom: Al Lone pair of electrons: 0 Number of bonded atoms: 3

Step 2: Use electron domain geometry to find the hybridization

We will now use the electron domain geometry for each molecule to determine the hybridization of the central atom. For molecule (a) \(H_2S\): Total electron domains: 2 (lone pair) + 2 (bonded) = 4 Geometry: Tetrahedral Hybridization: sp^3 For molecule (b) \(SeF_6\): Total electron domains: 0 (lone pair) + 6 (bonded) = 6 Geometry: Octahedral Hybridization: sp^3d^2 For molecule (c) \(P(OH)_3\): Total electron domains: 0 (lone pair) + 3 (bonded) = 3 Geometry: Trigonal planar Hybridization: sp^2 For molecule (d) \(AlI_3\): Total electron domains: 0 (lone pair) + 3 (bonded) = 3 Geometry: Trigonal planar Hybridization: sp^2 So, the hybridization of the central atoms for each molecule is: a) \(H_2S\): sp^3 b) \(SeF_6\): sp^3d^2 c) \(P(OH)_3\): sp^2 d) \(AlI_3\): sp^2

Key Concepts

Electron Domain Geometry

Understanding electron domain geometry is vital when it comes to predicting molecular shapes and hybridization. The term "electron domain" refers to areas around the central atom where electrons are likely to be found. These areas include bonds (single, double, or triple) and lone pairs of electrons.

To identify the electron domain geometry, it's essential to count both the bonding and lone pairs of electrons around the central atom. This count gives a total number of electron domains.

• The geometry helps us visualize the three-dimensional arrangement of these electron domains.
• The placement is such that electron domains are as far apart as possible, minimizing repulsion due to electron-electron interactions.
• The number and arrangement of these domains determine the molecular geometry.

For example, in a molecule like H extsubscript{2}S, there are four electron domains (2 bonds + 2 lone pairs), corresponding to a tetrahedral geometry. Even though not all domains may consist of bonds, the geometry refers to all charge clouds around the central atom.

Covalent Bonding Groups

Covalent bonding groups are crucial in understanding molecular structures. These groups form when atoms share pairs of electrons. This sharing of electrons allows each atom to attain the electron configuration of a noble gas, leading to stability.

The number of covalent bonding groups gives insight into the molecular shape and hybridization state of the central atom.

• Each single bond represents one covalent bonding group.
• Double and triple bonds also count as only one group.
• The number of bonding groups differs from the number of bonds as double and triple bonds are still one group due to their single point of electron sharing.

Consider SeF extsubscript{6}, with six covalent groups and no lone pairs, resulting in an octahedral geometry and a sp extsuperscript{3}d extsuperscript{2} hybridization. This highlights how the covalent bonding groups connect closely to predicting the molecule's geometry.

Central Atom in Molecules

The central atom in a molecule often holds the key to determining many of its properties, such as geometry, hybridization, and polarity. It is typically the atom that forms the most bonds and often, but not always, the least electronegative.

Several factors should be considered regarding the central atom:

• It’s the main point of reference in drawing Lewis structures, which helps visualize the distribution of electrons around the molecule.
• Through hybridization, the central atom combines its orbitals to accommodate the attached atoms and any lone pairs.
• In molecules like AlI extsubscript{3}, the central aluminum atom has three bonded iodides, with no lone pairs, indicating a trigonal planar configuration.

Being able to pinpoint the central atom allows us to effectively analyze molecular structures and properties, aiding our understanding of how molecules interact within themselves and with other molecules.