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Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 28a2

The figure that follows contains ball-and-stick drawings of three possible shapes of an AF4 molecule. (a) For each shape, give the electron-domain geometry on which the molecular geometry is based. ii.

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Identify the central atom in the AF4 molecule, which is typically the atom that is less electronegative and has the ability to form multiple bonds.
Determine the total number of electron domains around the central atom. This includes both bonding pairs (shared between atoms) and lone pairs (non-bonding pairs of electrons localized on the central atom).
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the electron-domain geometry based on the number of electron domains. Common geometries include linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral.
Compare the actual molecular geometry shown in the drawings with the idealized electron-domain geometry. Note how the presence of lone pairs or multiple bonds might distort the geometry from its ideal shape.
For each molecular shape provided, state the electron-domain geometry that would typically give rise to such a molecular arrangement, considering any deviations caused by factors like lone pairs or double bonds.

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Key Concepts

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

Electron-Domain Geometry

Electron-domain geometry refers to the spatial arrangement of all electron domains around a central atom in a molecule. This includes both bonding pairs of electrons (shared between atoms) and lone pairs (non-bonding electrons). The geometry is determined by the number of these electron domains, which influences the overall shape of the molecule.
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Molecular Geometry

Molecular geometry describes the three-dimensional arrangement of atoms in a molecule, focusing on the positions of the nuclei rather than the electron clouds. It is derived from the electron-domain geometry but takes into account the repulsion between electron pairs, leading to specific shapes such as linear, trigonal planar, or tetrahedral.
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VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of molecules based on the repulsion between electron pairs in the valence shell of the central atom. According to VSEPR, electron pairs will arrange themselves as far apart as possible to minimize repulsion, which directly influences both electron-domain and molecular geometries.
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