Multiple Choice
What is the molecular geometry around the nitrogen atom in CH3NH2?
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12. Molecular Shapes & Valence Bond Theory
Molecular Geometry
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What is the molecular geometry of PH3?
A
Trigonal planar
B
Bent
C
Trigonal pyramidal
D
Tetrahedral
Verified step by step guidance1
Identify the central atom in PH\3, which is phosphorus (P).
Determine the number of valence electrons on phosphorus: phosphorus has 5 valence electrons.
Count the number of bonded atoms and lone pairs on phosphorus: PH\3 has 3 hydrogen atoms bonded to phosphorus and 1 lone pair on phosphorus (since 5 valence electrons minus 3 bonding pairs leaves 1 lone pair).
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry: with 3 bonded atoms and 1 lone pair, the electron pair geometry is tetrahedral, but the molecular shape (ignoring the lone pair) is trigonal pyramidal.
Conclude that the molecular geometry of PH\3 is trigonal pyramidal, not trigonal planar, bent, or tetrahedral.
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