What is the geometry for five bonded atoms and no lone pairs?

• A. Trigonal bipyramidal
• B. Octahedral
• C. Tetrahedral
• D. Square pyramidal

Answer: (A)

In VSEPR theory, the shape around a central atom is determined by how many electron pairs are around it and whether any are non-bonding. If there are five bonding pairs and no lone pairs, the five positions around the central atom arrange themselves as a trigonal bipyramid: three positions lie in a plane (equatorial) at 120° from each other, and two positions lie along an axis (axial) 180° apart. With all five positions occupied by atoms, the molecule adopts a trigonal bipyramidal geometry.

This matches the situation of five bonds and zero lone pairs, so the geometry is trigonal bipyramidal. Other shapes correspond to different counts of electron pairs or the presence of lone pairs: six electron pairs give octahedral, four give tetrahedral, and a square pyramidal shape would require five bonds plus one lone pair, which isn’t the case here.