When an atom becomes a cation, what has occurred?

When an atom becomes a cation, it means that it has lost one or more electrons. A cation is defined as a positively charged ion, and this positive charge arises from the reduction in the number of negatively charged electrons relative to the number of positively charged protons in the nucleus. By losing electrons, the atom has an excess of protons compared to its electrons, which results in a net positive charge.

Understanding this process is crucial because it affects the atom's reactivity and how it interacts with other atoms or compounds. For instance, cations often engage in ionic bonding with anions (negatively charged ions), influencing chemical reactions and the properties of compounds.

The other concepts, while relevant in different contexts, do not accurately describe what occurs when an atom becomes a cation. Gaining electrons would result in an anion, nuclear fission refers to the splitting of an atomic nucleus, and changing chemical properties generally involves a broader range of changes in atomic or molecular structure, rather than just the loss of electrons.