The shape of the ammonia molecule, NH3, is
Correct answer: B. pyramidal, with a bond angle of about 107 degrees
- A. trigonal planar
- B. pyramidal, with a bond angle of about 107 degrees
- C. tetrahedral, with an angle of 109.5 degrees
- D. linear
Explanation
Nitrogen has three bond pairs and one lone pair, so the four electron regions point tetrahedrally but only the three bonded atoms are visible, giving a pyramid. The lone pair repels the bond pairs more strongly than they repel each other, so the angle is compressed from 109.5 to about 107 degrees. Describing a shape means naming the arrangement of the atoms, not of the electron pairs.
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About VSEPR Theory
Valence shell electron pair repulsion theory predicts molecular shape by arranging bonding pairs and lone pairs around a central atom to minimize repulsion. Questions cover linear, trigonal planar, tetrahedral, trigonal bipyramidal and octahedral electron geometries, bond angles and distortions caused by lone pairs. Electron geometry is not always the same as molecular shape.
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