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

Cations are formed by the loss of electrons, which is why this choice accurately describes their behavior compared to anions. When an atom loses one or more electrons, it becomes positively charged. This loss of negatively charged electrons results in a decrease in electron-electron repulsion within the atom, leading to a reduction in size of the electron cloud surrounding the nucleus. Consequently, cations are typically smaller than their parent atoms.

In contrast, anions are formed through the gain of electrons, which increases electron-electron repulsion and results in a larger size compared to the original atom. This fundamental distinction in the formation of cations and anions is critical for understanding their behavior in chemical reactions and their roles in different compounds.