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Classifying compounds as ionic or covalent

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Compounds containing two elements (so called binary compounds) can either have ionic or covalent bonding.

• If a compound is made from a metal and a non-metal, its bonding will be ionic.
• If a compound is made from two non-metals, its bonding will be covalent.

To decide if a binary compound has ionic or covalent bonding, first locate the two elements concerned in the Periodic Table and decide if they are metals (shown in blue) or non-metals (shown in pink).

If they are both non-metals (such as carbon and oxygen) they will form a covalent compound (such as carbon dioxide, CO₂).

If one is a metal (like sodium) and the other a non-metal (like fluorine), they will form an ionic compound (such as sodium fluoride, NaF).