Define electrophile and nucleophile

Electrophile is an ion or molecule that is electron deficient and can accept electrons. Electrophiles are often reducing agents and Lewis acids. They are either positive ions (e.g. NO²⁺) or molecules that have a positive charge on a particular atom (e.g. SO₃, which has an electron deficient sulphur atom). In organic reactions they tend to attack negatively charged parts of a molecule. Types of electrophiles: Lewis acids, cations and electron deficient sites in organic compounds

Nucleophile is an ion or molecule that can donate electrons. Nucleophiles are often oxidizing agents and Lewis bases. They are either negative ions (e.g. Cl^–) or molecules that have electron pairs (e.g. NH₃). In organic reactions they tend to attack positively charged parts of a molecule. Types of nucleophiles: Lewis bases, anions and electron rich sites in organic compounds.

Conceptual definition of acids and bases

Acids and Bases Definitions

The most common definitions of acids and bases are Arrhenius acids and bases, Brønsted-Lowry acids and bases, and Lewis acids and bases. 

Brønsted-Lowry acids and bases

• A Brønsted-Lowry base is a substance that accepts hydrogen ions during a chemical reaction. (Bases are proton acceptors)
• A Brønsted-Lowry acid is a substance that gives up hydrogen ions during a chemical reaction. (Acids are proton donors)

Arrhenius acids and bases

• An Arrhenius acid is a substance that when added to water increases the number of H⁺ ions in the water. Acid + H₂O → H₃O⁺ + conjugate base
• An Arrhenius base is a substance that when added to water increases the number of OH^- ions in the water. Base + H₂O → conjugate acid + OH^-

Lewis acids and bases

• A Lewis acid is a substance that is an electron pair acceptor.
• A Lewis base is a substance that is an electron pair donator.