Multiple Choice
What is the molecular geometry of OF2?
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12. Molecular Shapes & Valence Bond Theory
Molecular Geometry
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What is the molecular geometry of PH3?
A
Bent
B
Trigonal pyramidal
C
Tetrahedral
D
Trigonal planar
Verified step by step guidance1
Identify the central atom in PH3, which is phosphorus (P), and note that it is bonded to three hydrogen (H) atoms.
Determine the number of valence electrons on the phosphorus atom. Phosphorus is in group 15, so it has 5 valence electrons.
Count the total number of electron pairs around the phosphorus atom by adding the bonding pairs (3 P-H bonds) and any lone pairs. Since phosphorus has 5 valence electrons and forms 3 bonds, it has 1 lone pair.
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry. With 3 bonding pairs and 1 lone pair, the electron pair geometry is tetrahedral, but the molecular shape (considering only atoms) is trigonal pyramidal.
Conclude that the molecular geometry of PH3 is trigonal pyramidal due to the presence of one lone pair on phosphorus causing a distortion from a perfect tetrahedral shape.
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