Cation
Cation
A cation is any atom or group of atoms that has a net positive charge. While matter is electrically neutral overall, ionic compounds are matter composed of positively and negatively charged particles called ions— any atom or group of atoms with an overall electrical charge. According to the laws of physics, opposite charges attract, so the oppositely charged ions attract each other to form compounds that are, overall, electrically neutral. In such compounds, the number of positive charges on the cations equal the number of negative charges. Ions with an overall negative charge are called anions. Compounds composed of both cations and anions, such as table salt (sodium chloride, NaCl) and potash (potassium carbonate, K2 CO3), are ionic compounds.
Cations are formed when an atom or group of atom loses one or more electrons, producing more protons than electrons and resulting in an overall positive charge. (Each proton has a +1 charge, and each electron has a -1 charge. In normal atoms, the number of protons equals the number of electrons, so a normal atom has an overall charge of zero. We say it is electrically neutral.) Anions, on the other hand, are formed when an atom or group of atoms accepts one or more electrons, so it has more negative than positive charges. Most metallic elements react chemically to form cations, losing electrons. Most nonmetallic elements react chemically to gain electrons, forming anions.
See also Anion.