An ion is an electrically charged particle. Cations have a positive charge. Anions have a negative charge. The charge on a monoatomic anion depends on the group for the atom.
Nonmetal elements have greater attractions for electrons and tend to gain electrons to form anions.
The charge on the ion is written as a superscript after the element symbol. For example chlorine gains one electron to form chloride, Cl 1- . Sulfur gains two electrons to form sulfide, S 2- . You can predict the negative charge on an anion by looking at the group number for the atom. The charge for representative elements is typically equal to the group number minus eight.