The shape of the ammonia molecule, NH3, is

  • 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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