Which geometry corresponds to three bonded atoms and one lone pair?

• A. Tetrahedral
• B. Trigonal planar
• C. Bent
• D. Pyramidal

Answer: (D)

In VSEPR, the shape around a central atom is determined by the number of electron domains (bonding pairs plus lone pairs). Four electron domains arrange in a tetrahedral pattern, but if one of those domains is a lone pair, the three bonding pairs are pushed into a pyramid shape. That gives a pyramidal geometry for the molecule, specifically trigonal pyramidal, which matches three bonded atoms with one lone pair. The other shapes don’t fit: four bonding pairs produce a tetrahedral arrangement, three bonds with no lone pair would be trigonal planar, and two bonds with a lone pair produce a bent shape.