Acid and base
Acid according to Brønsted: A compound that can donate protons (H+)
Base according to Brønsted: A compound that can accept protons (H+)
Acid according to Lewis (Lewis acid): A compound that can accept an electron pair
Base according to Lewis (Lewis base): A compound that can ‘donate’ an electron pair
Carbocations are strong Lewis acids.
Carbanions are strong bases (both Lewis and Brønsted).
Carbocations, carbanions and carbon radicals are reactive and participate in chemical reactions.