What is the basic assumption of VSEPR theory?

The basic assumption of VSEPR (Valence Shell Electron Pair Repulsion) theory is that regions of electron density, such as bonds and lone pairs, minimize repulsion by maximizing their distance from each other. This principle is grounded in the idea that electrons are negatively charged and, as such, will repel one another. The arrangement of these electron pairs around a central atom is determined by this repulsive interaction, leading to specific molecular geometries.

For example, in a molecule like methane (CH₄), the four hydrogen atoms arranged around the central carbon atom maximize their distance from one another due to the repulsions between the bonding pairs of electrons. The arrangement results in a tetrahedral geometry, as this configuration provides the optimal distance between the regions of electron density.

The other options do not accurately capture the essence of VSEPR theory. While molecules do have geometrical structures influenced by distances, the core assumption focuses specifically on the repulsive interactions among electron densities, rather than the rigidity of molecules or the fact that electrons are paired in orbitals.