1.28 Describe the formation of ions by the gain or loss of electrons .

Ions are like positive or negatively charged versions of atoms. If an atom loses an electron in a reaction, it becomes positive in relation to the amount of electrons it has lost. If an atom gains an electron, it becomes negative in the same way. I.e. if Potassium reacts with something, it will lose one electron (it only has one in its outer shell) and will become +1. Atoms react in an attempt to fill their outer shells so they can be more stable.