Chapter 2 - Atoms, Molecules, and Ions - Active Learning Questions - Page 73: 15

c) Adding or subtracting electrons to/from an atom

Ions are atoms that have an overall charge that is less than or greater than zero. That means that the atom contains fewer or a greater number of electrons than the number of protons. Thus, adding or subtracting electrons to or from an atom will give that atom a non-zero charge and form an ion.