A reagent that brings an electron pair is called a nucleophile (Nu:) i.e., nucleus seeking and the reaction is then called nucleophilic.
Examples of nucleophiles are the negatively charged ions with lone pair of electrons such as hydroxide (HO– ), cyanide (NC–) ions and carbanions (R3C:–).
A reagent that takes away an electron pair is called electrophile (E+) i.e., electron seeking and the reaction is called electrophilic.
Examples of electrophiles include carbocations ( CH3+) and neutral molecules having functional groups like carbonyl group (>C=O) or alkyl halides(R3C-X, where X is a halogen atom).
