Multiple Choice
Which molecular geometry best describes the shape of the ammonium ion, NH_4^+?
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12. Molecular Shapes & Valence Bond Theory
Molecular Geometry
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Which molecular geometry best describes the arrangement of atoms in the PF5 molecule?
A
Square planar
B
Tetrahedral
C
Trigonal bipyramidal
D
Octahedral
Verified step by step guidance1
Identify the central atom in the molecule, which is phosphorus (P) in PF5.
Determine the number of valence electrons around the central atom. Phosphorus has 5 valence electrons, and each fluorine atom contributes 1 electron for bonding, totaling 5 bonds.
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry. Since there are 5 bonding pairs and no lone pairs on phosphorus, the electron pairs will arrange themselves to minimize repulsion.
Recall that 5 bonding pairs around a central atom arrange in a trigonal bipyramidal geometry, with three atoms in an equatorial plane and two atoms in axial positions.
Conclude that the molecular geometry of PF5 is trigonal bipyramidal, not square planar, tetrahedral, or octahedral.
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