What is the electron geometry for a molecule with three regions of high electron density (rheds) surrounding the central atom?

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

Answer: (D)

Verified step by step guidance

1. Identify the number of regions of high electron density (RHEds) around the central atom. In this problem, there are three RHEds.
2. Recall that electron geometry describes the spatial arrangement of all electron regions (bonding and lone pairs) around the central atom, not just the bonded atoms.
3. Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to determine the electron geometry. According to VSEPR, three regions of electron density arrange themselves as far apart as possible in a plane, forming a trigonal planar geometry.
4. Understand that the options given include 'Tetrahedral' (which corresponds to four RHEds), 'Bent' (which is a molecular shape, not electron geometry, often with two bonded atoms and one or more lone pairs), and 'Linear' (which corresponds to two RHEds).
5. Conclude that for three regions of electron density, the correct electron geometry is 'Trigonal planar', where the electron regions are arranged at approximately 120° angles in a flat plane.