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Ionisation is a process by which an atom or molecule gain or lose an electron hence acquiring a positive or negative charge. The formation of anion and cation occurs in this process.Ionisation occurs when a sufficiently energetic charged particle travel through gases, liquids,or solids. For example, when metallic zinc is exposed to acid it loses electrons and therefore becomes positively charged.The amount of energy required to remove an electron from the valence shell of an atom is called the ionisation enthalpy.

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