Another type of bond is the result of attraction between ions of opposite charge. Ions are atoms that have gained or lost electrons. Sodium, on the left, has shells with electrons numbering 2, 8, and 1; chlorine, on the right, has 2, 8, and 7. Sodium would have a full outer shell if it lost the single electron in its third shell, chlorine’s would be full if it gained one. An electron is transferred from sodium to chlorine. Sodium is now Na⁺, chlorine is Cl^-. The electrical attraction between them is an ionic bond.