* A metal (cation): This is the positively charged ion, which is formed when a metal atom loses electrons.

* A nonmetal (anion): This is the negatively charged ion, formed when a nonmetal atom gains electrons.

Key points:

* Opposite charges attract: The positively charged metal ion and the negatively charged nonmetal ion are attracted to each other due to electrostatic forces, forming a strong ionic bond.

* Neutral compound: The overall compound must be electrically neutral. This means the number of positive charges from the metal cation must equal the number of negative charges from the nonmetal anion.

* Fixed ratios: The ratio of metal to nonmetal ions in the compound is fixed, determined by the charges on the ions.

Examples:

* NaCl (Sodium chloride): Sodium (Na) is a metal and forms a +1 cation (Na+), while chlorine (Cl) is a nonmetal and forms a -1 anion (Cl-).

* MgO (Magnesium oxide): Magnesium (Mg) is a metal and forms a +2 cation (Mg2+), while oxygen (O) is a nonmetal and forms a -2 anion (O2-).

* KBr (Potassium bromide): Potassium (K) is a metal and forms a +1 cation (K+), while bromine (Br) is a nonmetal and forms a -1 anion (Br-).

Important Note: There are exceptions to these rules, such as compounds containing polyatomic ions (ions made of multiple atoms).