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What is covalent bond?

A covalent bond is a shared pair of electrons between two non-metal atoms, held together by attraction to both nuclei.

Covalent bond explained

Simple molecular substances have strong covalent bonds inside molecules but weak intermolecular forces between them, giving low melting points.
Giant covalent structures such as diamond and silicon dioxide have covalent bonds throughout the lattice, so they melt at extremely high temperatures.

Key formula

Shared pair: H ⁣: ⁣H\mathrm{H}\!:\!\mathrm{H}

Worked example

Methane, CH₄, has four single covalent bonds and a bond angle of 109.5∘109.5^{\circ}.

Examiner tip

When explaining low boiling points, say the weak intermolecular forces are overcome — never say covalent bonds break. That error caps the mark.

Covalent bond: common questions

Why do simple molecular substances not conduct electricity?
They have no free ions or delocalised electrons, so there are no mobile charge carriers.
What is a dative covalent bond?
A covalent bond in which both shared electrons come from the same atom, as in the ammonium ion.

Related terms

Ionic bond

An ionic bond is the strong electrostatic attraction between oppositely charged ions formed when electrons transfer from a metal to a non-metal.

Electronegativity

Electronegativity is the ability of an atom to attract the shared pair of electrons in a covalent bond towards itself.

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