Final answer:
Atoms undergo ionization to become stable ions, either becoming cations by losing electrons or anions by gaining electrons to fulfill the octet rule. An example is the formation of an oxide ion from an oxygen atom, which achieves a stable configuration by gaining two electrons.
Step-by-step explanation:
When atoms become stable ions, they undergo a process called ionization. Ionization can result in the formation of a cation or an anion. Cations are positively charged ions that result from the loss of electrons, and anions are negatively charged ions that result from the gain of electrons. Atoms achieve stability by obeying the octet rule, which generally means having eight electrons in their outermost shell, resembling the electron configuration of a noble gas. This often involves the transfer of electrons to or from other atoms to fill or empty the valence shell.
To make a neutral atom of Oxygen-16, one would combine 8 protons, 8 neutrons, and 8 electrons. The isotope symbol for this atom would be 16O. Adding two more electrons would create an oxide ion, O2-, which is a stable anion because it now has a full outer electron shell.