Some general points can be made about ionic compounds:

The smallest unit of an ionic compound is a formula
unit. The mass of this formula unit is called the formula
mass. ( We will discuss more about formula mass in section
7.1.)

The formula unit of sodium chloride is NaCl. It has a formula mass
is 58.44 amu/formula unit.

The formula unit of sodium chloride is MgCl_{2}. It has a formula
mass is 95.21 amu/formula unit.

The strong attractions between the cations and the anions in ionic solids
are responsible for their high melting points. For ionic compounds, melting
points typically range from 300^{o}C to 1000^{o}C.

This means that when NaCl is dissolved in water, the solution contains
Na^{+} ions and Cl^{-} ions.

The dissociated ions in aqueous solution gives the solution the ability
to conduct electricity. Therefore, ionic compounds dissolved in water makes
strong electrolytes.