So we have the acid molecule that donates an H plus ion and a bond is broken while the other molecule, the base, accepts that H plus ion because it has a lone pair of electrons and it forms a Covalent bond. So in an aft base reaction, we have an exchange of a proton. And the reason we say a proton is because a hydrogen ion lacks an electron and it only has a proton in the nucleus. So in any acid base reaction we have a hydrogen atom that is exchanged between our two molecules, the acid in the base. And at the same time, one Covalent bond is broken and another Covalent bond is actually formed. So let's suppose we have some hypothetical acid ha where A is simply an atom or a group of atoms that are attached to our H atom and this is a Covalent bond.