What Is a Lewis Acid and a Lewis Base? (HL)

A Lewis acid is an electron-pair acceptor, while a Lewis base is an electron-pair donor. When they react, the Lewis base donates both electrons that form a new coordination bond.

This is Additional Higher Level content in Reactivity 3.4, Electron-pair sharing reactions.

How the reaction works

A Lewis base must have an available electron pair, usually a lone pair. A Lewis acid must have somewhere to accept that pair, such as an incomplete valence shell, a vacant orbital, or a positive charge.

For example, ammonia reacts with boron trifluoride:

$\text{NH}_3(g) + \text{BF}_3(g) \rightarrow \text{H}_3\text{NBF}_3(g)$

What Is a Lewis Acid and a Lewis Base? (HL)

A Lewis acid is an electron-pair acceptor, while a Lewis base is an electron-pair donor. When they react, the Lewis base donates both electrons that form a new coordination bond.

This is Additional Higher Level content in Reactivity 3.4, Electron-pair sharing reactions.

How the reaction works

For example, ammonia reacts with boron trifluoride:

$\text{NH}_3(g) + \text{BF}_3(g) \rightarrow \text{H}_3\text{NBF}_3(g)$

Species	Lewis behavior	Reason
$\text{NH}_3$	Base	Nitrogen donates a lone pair
$\text{OH}^-$	Base	Oxygen donates a lone pair
$\text{BF}_3$	Acid	Boron has an incomplete octet
$\text{H}^+$	Acid	Accepts an electron pair
Metal cation	Acid	Accepts electron pairs from ligands
Ligand	Base	Donates an electron pair to a metal cation

What Is a Lewis Acid and a Lewis Base? (HL)

How the reaction works

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What Is a Lewis Acid and a Lewis Base? (HL)

How the reaction works

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