If the ion is named by (element-name) + ion, it is the element with a positive charge. This means: Sodium ion: Na(1+) Aluminum ion: Al(3+) If the ion is named by (element-prefix)+ide, then it has a negative charge. This means: Chloride: Cl(1-) Nitride: N(3-) Finally, if it has roman numerals after the name, that is the amount of positive charge the ion has. Therefore: Iron (II): Fe(2+) Iron(III): Fe(3+)
