Ionic compound

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⁻.

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.

	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	N^3-	O^2-	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

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

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