Cations are ions that are positively charged. Anions are ions that are negatively charged. Some common cations include: Na+, K+, Ca2+, Mg2+, and Fe2+.  Common anions include: Cl-, Br-, F-, I-, O2-, N3-, and S-. These ions can form ionic compounds such as NaCl, KCl, NaBr, NaF, and NaI.