Physics: Ions

Ions are chemical species having positive or negative charge. They are never neutral.

When an atom loses or gains an electron or electrons, it forms an ion.

Ions are of two types, positive and negative.

Positive ions are called cations.

Negative ions are called anions.

Note: Often, there are ions comprising groups of atoms. Still, they are either positive or negative, but never neutral.

Elements need to be stable. A duplet(2 electrons in the first shell) or octet(8 electrons in its last shell) electronic configuration is required. In order to be stable elements gain or lose electrons forming ions. For example a Beryllium atom has a configuration of 2,2 or 2s2. It needs to lose two valence electrons so that it can have a duplet configuration.