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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Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 88d
Consider the molecule PF4Cl. (d) Would you expect the molecule to distort from its ideal electron-domain geometry? If so, how would it distort?
Verified step by step guidance1
Identify the central atom in the molecule PF4Cl, which is phosphorus (P).
Determine the electron-domain geometry around the central atom based on the number of electron groups (bonds and lone pairs). Phosphorus in PF4Cl has five electron groups (four F atoms and one Cl atom bonded to it), suggesting a trigonal bipyramidal electron-domain geometry.
Consider the positions of the atoms in the trigonal bipyramidal geometry. The positions include two axial and three equatorial sites.
Analyze the differences in electronegativity between the fluorine (F) and chlorine (Cl) atoms. Fluorine is more electronegative than chlorine.
Predict the distortion: Since F is more electronegative than Cl, F atoms will occupy the equatorial positions to minimize repulsion, and the Cl atom will occupy one of the axial positions. This arrangement can lead to a slight distortion from the ideal trigonal bipyramidal geometry due to differences in bond angles caused by the different atoms.
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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 electron pairs around a central atom, which can include bonding pairs and lone pairs. In the case of PF4Cl, the central phosphorus atom is surrounded by five electron domains (four fluorine atoms and one chlorine atom), leading to a trigonal bipyramidal geometry according to VSEPR theory.
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Steric Effects
Steric effects arise from the repulsion between electron clouds of atoms or groups in a molecule. In PF4Cl, the presence of different atoms (F and Cl) can lead to variations in bond angles and distances due to their differing sizes and electronegativities, which can cause the molecule to distort from its ideal geometry.
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Lone Pair Repulsion
Lone pair repulsion is a significant factor in molecular geometry, as lone pairs occupy more space than bonding pairs. Although PF4Cl does not have lone pairs on the phosphorus atom, the differing electronegativities and sizes of the bonded atoms can still lead to distortions in the ideal geometry, affecting bond angles and overall shape.
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Related Practice
Textbook Question
Consider the molecule PF4Cl. (a) Draw a Lewis structure for the molecule, and predict its electron-domain geometry.
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)?
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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?
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Textbook Question
Fill in the blank spaces in the following chart. If the molecule column is blank, find an example that fulfills the conditions of the rest of the row. Molecule Electron-Domain Hybridization Dipole Geometry of Central Atom Moment? Yes or No CO2 sp3 Yes sp3 No Trigonal planar No SF4 Octahedral No sp2 Yes Trigonal bipyramidal No XeF2
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