Textbook Question
Consider the following XF4 ions: PF4-, BrF4-, ClF4+, and AlF4-. (a) Which of the ions have more than an octet of electrons around the central atom?
Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 88a
Consider the molecule PF4Cl. (a) Draw a Lewis structure for the molecule, and predict its electron-domain geometry.
Verified step by step guidance1
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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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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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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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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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Related Practice
Textbook Question
Consider the following XF4 ions: PF4-, BrF4-, ClF4+, and AlF4-. (b) For which of the ions will the electron-domain and molecular geometries be the same?
Textbook Question
Consider the following XF4 ions: PF4-, BrF4-, ClF4+, and AlF4-. (c) Which of the ions will have an octahedral electron-domain geometry?
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Textbook Question
Consider the molecule PF4Cl. (c) Predict the molecular geometry of PF4Cl. How did your answer for part (b) influence your answer here in part (c)?
Textbook Question
Consider the molecule PF4Cl. (d) Would you expect the molecule to distort from its ideal electron-domain geometry? If so, how would it distort?
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Textbook Question
Although I3- is a known ion, F3- is not. (d) Yet another classmate says F3- does not exist because F is too small to make bonds to more than one atom. Is this classmate possibly correct?