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Ch.9 - Molecular Geometry and Bonding Theories
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Capitolo 9, Problema 88a

Consider the molecule PF4Cl. (a) Draw a Lewis structure for the molecule, and predict its electron-domain geometry.

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Step 1: Count the total number of valence electrons available for the molecule PF4Cl. Phosphorus (P) has 5 valence electrons, each fluorine (F) has 7 valence electrons, and chlorine (Cl) also has 7 valence electrons. Therefore, the total number of valence electrons is calculated as follows: 5 (from P) + 4 * 7 (from F) + 7 (from Cl).
Step 2: Arrange the atoms with phosphorus (P) as the central atom since it is less electronegative than fluorine (F) and chlorine (Cl). Connect each of the four fluorine atoms and the chlorine atom to the phosphorus atom using single bonds.
Step 3: Distribute the remaining valence electrons to satisfy the octet rule for each atom. Start by completing the octets of the fluorine and chlorine atoms, which typically require 8 electrons in total (including the bonding electrons).
Step 4: Check the electron count around the central phosphorus atom. Phosphorus can have more than 8 electrons due to its ability to expand its octet. Ensure that all valence electrons are used and that the structure is stable.
Step 5: Predict the electron-domain geometry based on the arrangement of electron pairs around the central phosphorus atom. With five regions of electron density (four bonds with fluorine and one with chlorine), the electron-domain geometry is trigonal bipyramidal.

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Lewis Structure

A Lewis structure is a diagram that represents the bonding between atoms in a molecule and the lone pairs of electrons that may exist. It uses dots to represent valence electrons and lines to represent bonds between atoms. Drawing a Lewis structure involves determining the total number of valence electrons, arranging the atoms, and ensuring that each atom achieves a stable electron configuration, typically following the octet rule.
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Lewis Dot Structures: Ions

Electron-Domain Geometry

Electron-domain geometry refers to the spatial arrangement of all electron domains (bonding and lone pairs) around a central atom in a molecule. This geometry is determined by the number of electron domains, which can be single bonds, double bonds, triple bonds, or lone pairs. The VSEPR (Valence Shell Electron Pair Repulsion) theory is used to predict the geometry, as it states that electron domains will arrange themselves to minimize repulsion.
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Electron Geometry

VSEPR Theory

VSEPR theory is a model used to predict the shape of molecules based on the repulsion between electron pairs surrounding a central atom. According to this theory, the arrangement of electron domains around the atom will adopt a geometry that minimizes repulsion, leading to specific molecular shapes such as linear, trigonal planar, tetrahedral, and octahedral. Understanding VSEPR is crucial for predicting the three-dimensional structure of molecules like PF4Cl.
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Molecular Shapes and VSEPR