Which of the following is NOT an electronic geometry as described by VSEPR theory?

• A. Linear
• B. Tetrahedral
• C. Trigonal bipyramidal
• D. Trigonal pyramidal

Answer: (D)

Verified step by step guidance

1. Recall that VSEPR (Valence Shell Electron Pair Repulsion) theory describes the electronic geometry based on the number of electron groups (bonding and lone pairs) around a central atom.
2. Identify the common electronic geometries according to VSEPR theory: Linear, Tetrahedral, Trigonal bipyramidal, Octahedral, etc. These geometries describe the arrangement of electron groups, not just atoms.
3. Understand that 'Trigonal pyramidal' is a molecular geometry, not an electronic geometry. It arises when there are three bonding pairs and one lone pair, causing the shape of the atoms to be pyramidal, but the electronic geometry remains tetrahedral because it counts all electron groups.
4. Compare the options: Linear, Tetrahedral, and Trigonal bipyramidal are all electronic geometries describing the arrangement of electron groups, while Trigonal pyramidal describes the shape of atoms after considering lone pairs.
5. Conclude that 'Trigonal pyramidal' is NOT an electronic geometry but a molecular geometry, making it the correct answer to the question.