Ionic compound

In chemistry, an ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. To form an ionic compound, there needs to be at least one metal and one non-metal. The metal element is usually the positive charge and the non-metal element is a negative charge.

Ions can be single atoms, as in common table salt sodium chloride, or more complex groups such as calcium carbonate. But to be considered ions, they must carry a positive or negative charge.

Thus, in an ionic bond, one 'bonder' must have a positive charge and the other a negative one. By sticking to each other, they resolve, or partially resolve, their separate charge imbalances. Positive to positive and negative to negative ionic bonds do not occur. (For a real world analogy, experiment with a pair of bar magnets.)

Ionic compounds generally have high melting and boiling points. They have good electrical conductivity when molten or in solution. While ionic inorganic compounds are solids at room temperature and will usually form crystals, organic ionic liquids are increasingly of interest.

When an ionic compound is named, the cation is named first and then the anion. When an elemental anion is named the suffix, -ide is added to the name of the element. There are two common types of cations: Type I and Type II. Type I cations have only one charge and their name is simply listed when the compound is named. Type II cations have more than one charge and when the ionic compound is named, a Roman numeral is used to denote the charge of the cation. In addition, there are common polyatomic anions which do not have suffixes in their name such as hypochlorite (ClO-).