Many of the elements on the periodic table will always form ions that have the same charge. The alkali metals (shown in yellow) always form +1 ions. The alkaline earth metals (red) always form +2 ions. The halogens (blue) always form -1 ions. The calcogens (green) form -2 ions.
Many of the transition metals (orange) can have more than one charge. The notable exceptions are zinc (always +2), silver (always +1) and cadmium (always +2).
