Covalent Bonding

This lesson covers covalent bonding — the sharing of electron pairs between non-metal atoms — as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand how covalent bonds form, draw dot-and-cross diagrams for simple molecules, and recognise common covalent substances.

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What Is Covalent Bonding?

A covalent bond is a shared pair of electrons between two non-metal atoms. Both atoms contribute one electron to the shared pair.

Covalent bonding occurs between non-metals only. It happens because non-metal atoms need to gain electrons to achieve a full outer shell, and they do this by sharing rather than transferring.

How a Covalent Bond Forms

1. Two non-metal atoms each have incomplete outer electron shells.
2. Their outer shells overlap.
3. A pair of electrons (one from each atom) is shared in the overlap region.
4. Both atoms now count the shared pair as part of their outer shell, achieving a full outer shell.
5. The shared electrons are attracted to the nuclei of both atoms — this attraction holds the atoms together.