When do ionic bonds occur?

Such a bond forms when the valence (outermost) electrons of one atom are transferred permanently to another atom. The atom that loses the electrons becomes a positively charged ion (cation), while the one that gains them becomes a negatively charged ion (anion). A brief treatment of ionic bonds follows.

Explanation:

Ionic bonds are formed between a metal and non-metal, for example sodium chloride. An atom of sodium will lose an electron and form a positive ion. An atom of chlorine will gain an electron and form a negative ion.

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