An atom that loses an electron is called a positive ion. An electron is a negatively charged particle, and the atom becomes positively charged upon its removal. An atom that loses an electron has more protons than electrons.
An atom that gains an electron adds a negative charge and becomes a negative ion. A negative ion contains more electrons than protons, resulting in the negative charge.
Sodium, potassium, calcium and iron are common examples of positive ions. Chloride and phosphorous are two types of negative ions. A molecule such as sodium chloride is a combination of positive and negative ions.