Ionic compound

chemical compound involving ionic bonding

In chemistry, an ionic compound is a compound made of ions. They have strong ionic bonds between particles. Lots of energy (heat) is required to break the bond apart, resulting in high melting and boiling points. The ions join because they have different charges. Compounds of metals and non-metals are usually ionic. They are made when two or more atoms come close together and an electron goes from one atom to the other atom. The electron does this because both atoms want a full outer shell, similar to those of the noble gases.

The crystal structure of sodium chloride, NaCl, a typical ionic compound. The purple spheres are sodium cations, Na+, and the green spheres are chloride anions, Cl.
Group I Group II Group III Group IV Group V Group VI Group VII Group VIII
Example Element Na Mg Al C N O Cl He
Charge 1+ 2+ 3+ See Note 1 3- 2- 1- See Note 2
Symbol of Ion Na+ Mg2+ Al3+ See Note 1 N3- O2- Cl- See Note 2

Note 1: carbon and silicon in Group 4 usually form covalent bonds by sharing electrons.

Note 2: the elements in Group 0 do not react with other elements to form ions

Physical properties change

Physical Properties Ionic Compounds
State at room temperature Solid
Electrical conductivity As Solid: No

Liquid (melted): Yes

Dissolved in solution: Yes (if soluble)

Boiling point and Melting Point High
Solubility in water Often high
Heat conductivity Low