The atom
Nitrogen gaining electrons

Nitrogen needs three electrons to fill the outer energy level. It will get three electrons from another atom.

Notice how the nitrogen atom takes three electrons. The imbalance of protons and electrons now creates a charge of -3 on the atom.

Atoms with a charge are known as IONS. More precisely atoms with a positive charge are known as cations while atoms with a negative charge are known as anions. Nitrogen, above, forms an anion.