Ionisation - GCSE Chemistry Definition

Ionisation is the process where an atom or molecule gains or loses electrons, resulting in a particle with a positive or negative charge, called an ion. When an atom loses one or more electrons, it becomes a positively charged ion, because it has more protons than electrons. Conversely, if an atom gains electrons, it becomes a negatively charged ion, as it has more electrons than protons. This process is important in chemistry, as it helps explain how substances react and form compounds. For example, Magnesium loses two electrons to form a Mg²⁺ ion: Mg → Mg²⁺ + 2e⁻. Ionisation can happen naturally or be caused by energy inputs like heat or light.