# Lewis baseZoomA-Z

The Lewis base as a nucleophilic molecule or ion is donating a free pair of electrons to an electron acceptor (Lewis acid) to form a covalent bond.

Examples of Lewis bases are $NH3$, $H2O$, $F−$, $N2$.

Bases are differentiated between hard and soft bases. The smaller, more electronegative (less polarizable) and higher oxidized a base is the harder it is.

The product from the combination of a Lewis base and a Lewis acid is called an acid-base complex, coordination compound or electron pair-acceptor-donor complex. Acid-base complexes formed from hard bases and hard acids or from soft bases and soft acids are more stable than complexes from hard acids and soft bases or vice versa.

See also: Lewis acid , Brønsted base , Brønsted acid