An acid is a molecule/ion which can accept an electron pair with the formation of a coordinate bond.
Acid → e– pair acceptor
Ex: Electron deficient molecules : BF3, AlCl3
Cations : H+ , Fe2+, Na+
Molecules with vacant orbitals : SF4, PF3
A base is any molecule/ion which has a lone pair of electrons which can be donated.
Base → (One electron pair donate)
Ex: Molecules with lone pairs : NH3 , PH3 , H2O, CH3OH
