When one atom supplies both bonding electrons

4 minAS Level3.7.1

AI-drafted, independently checked · not yet teacher-reviewed

By the end of this lesson

By the end, you can show where both electrons in a coordinate bond came from.

A shared pair with one donor

In an ordinary covalent bond, each atom supplies one electron to the shared pair. In a coordinate (dative covalent) bond, one atom supplies both electrons in the shared pair.

After the bond forms, it is still a covalent bond. The dots and crosses just let us trace where the pair started.

A lone pair is two outer-shell electrons on one atom that are not shared in a bond.

Worked example: Ammonia makes ammonium

Ammonia gas reacts with hydrogen chloride gas to form ammonium chloride. Show how nitrogen's lone pair forms the new N–H bond.

Have a go first?

The sketch isolates the new N–H bond; in the syllabus reaction, chloride is the counter-ion. All four N–H bonds in NH₄⁺ are equivalent.

Track the donated pair

Multiple choiceQuestion 1 · Recall

In a coordinate bond, how many atoms supply electrons to the shared pair?

AOne atom supplies both electrons.BEach atom supplies one electron.CNo atom supplies electrons.DThree atoms supply one electron each.

Fill in the blanksQuestion 2 · Apply

In NH₃ + HCl → NH₄⁺ + Cl⁻, the atom supplies both electrons for the new N–H bond, using its .

Answer the 2 questions above to continue.

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