For example:
Like ammonia, nitrogen atom of amines is trivalent and
carries an unshared pair of electrons Nitrogen orbitals
in amines are therefore, sp3 hybridised and the geometry
of amines is pyramidal Each of  the three sp3 hybridised
orbitals of nitrogen overlap with orbitals of hydrogen or
carbon depending upon the composition of the amines The fourth orbital of nitrogen in all amines contains an
unshared pair of electrons