A cation is an atom or group of atoms that has lost one or more electrons, becoming positively charged. The term “cation” comes from the Greek word for “going up.” When an atom loses an electron, it becomes a cation because it now has a higher energy level than it did before.
Cations are important in many chemical reactions, especially those involving acids and bases. For example, when hydrochloric acid (HCl) is added to water (H2O), the H+ ions from the acid combine with the OH- ions from the water to form H2O molecules. This reaction is called neutralization because it results in a solution with no net charge.
Cations can also be used to remove negative charges from other molecules. For example, when sodium hydroxide (NaOH) is added to water, the Na+ ions combine with OH-ions to form H2O molecules. This leaves behind any negatively charged molecules that were present in the solution originally. These negatively charged molecules are called anions.