Ions are expressed by the Chemical Symbol of the element(s) followed by a superscript of the charge the ion carries.  For example an Oxide ion would be `O^(2-)` Oxide is an oxygen anion which gains 2 electrons taking on a -2 electrical charge.  A sodium ion would be `Na^+` Sodium is a metallic cation which loses 1 electron taking on a +1 electrical charge. 

The chemical symbol of Silver is Ag.  Silver(I) loses one electron giving it a +1 charge.  Expressed as `Ag^+` This differs from Silver(II) which loses two electrons giving it a +2 charge, and is expressed as `Ag^(2+)`