A nucleophile is a
molecule which attracts other molecules that are
electron-deficient (
electrophiles). Nucleophiles will usually have
lone pairs of electrons that are aligned to increase their
electrostatic attraction according to the
Valence shell electron pair repulsion theory, making them
polar (or sometimes
amphipathic).
An everyday example of a nucleophile is water. In its normal alignment, water looks like this:
**O**
/ \
/ \
H H
With the stars representing lone pairs of electrons. Electrophiles will be attracted to the negative pole of the water molecule and join with an
ionic bond.