To dissociate means to take apart.

When ionic compounds (compounds made from metals and non-metals) like sodium chloride ##”NaCl”## or iron(III) sulfate ##”Fe”_2(“SO”_4)_3## are dissolved in water, they come apart into positive (metal) ions and negative (non-metal) ions.

When you write a dissociation reaction you separate the two ions, place their charges above their symbols, and then balance the entire equation.

For example, the dissociation of sodium chloride would look like this:

##”NaCl” → “Na”^+ + “Cl”^-##

The dissociation of iron(III) sulfate would look like this:

##”Fe”_2(“SO”_4)_3 → 2″Fe”^(3+) + 3″SO”_4^(2-)##