• An ion is an?electrically?charged?atom or group of atoms formed by the?loss?or?gain?of?electrons
• This loss or gain of electrons takes place to obtain a?full?outer?shell?of electrons
• The electronic structure of ions of elements in groups 1, 2, 3, 5, 6 and 7 will be the same as that of a noble gas - such as helium, neon, and argon
• Negative ions are called?anions?and form when atoms?gain?electrons, meaning they have more electrons than protons
• Positive ions are called?cations?and form when atoms?lose?electrons, meaning they have more protons than electrons
• All metals?lose?electrons to other atoms to become positively charged ions
• All non-metals?gain?electrons from other atoms to become negatively charged ions

Diagram showing the formation of the sodium ion

Diagram showing the formation of the chloride ion