Multiple Choice
What is the electron-pair geometry around the sulfur atom in SF_4?
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12. Molecular Shapes & Valence Bond Theory
Electron Geometry
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What is the electron geometry for phosphorus trihydride (PH_3)?
A
Tetrahedral
B
Trigonal planar
C
Trigonal pyramidal
D
Linear
Verified step by step guidance1
Identify the central atom in the molecule PH_3, which is phosphorus (P).
Determine the number of valence electrons around the phosphorus atom. Phosphorus has 5 valence electrons, and each hydrogen contributes 1 electron, for a total of 8 electrons to consider in bonding and lone pairs.
Draw the Lewis structure of PH_3: phosphorus forms three single bonds with three hydrogen atoms, and there is one lone pair of electrons remaining on phosphorus.
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the electron geometry. Count both bonding pairs and lone pairs around the central atom. Here, there are 3 bonding pairs and 1 lone pair, making 4 regions of electron density.
Since there are 4 regions of electron density, the electron geometry is tetrahedral, even though the molecular shape (considering only atoms) is trigonal pyramidal.
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