ACS Chemistry Practice Exam 2026 – The All-in-One Guide to Exam Success!

In a molecule with 6 electron domains, the arrangement of these domains is based on the principles of VSEPR (Valence Shell Electron Pair Repulsion) theory, which states that electron pairs arrange themselves to minimize repulsive forces. When one of these domains is a nonbonding pair (also known as a lone pair), it affects the overall geometry.

For a total of 6 electron domains, the ideal arrangement is octahedral, which has bond angles of 90 degrees between adjacent positions. In this scenario, even though one of the domains is a lone pair, the presence of the other 5 bonded atoms leads to the determination that the electron domain geometry remains octahedral. The lone pair will take up one position in the octahedral coordination, leading to a molecular geometry that might differ (like square pyramidal or square planar), but the arrangement of the electron domains as a whole is still classified as octahedral. Thus, the correct identification of the electron domain geometry is octahedral.