Greg Wah 24:05 “always has to have a hydrogen at the start … to be an acid” not A Lewis acid which is a species that accepts a pair of electrons from another species; in other words, it is an electron pair acceptor. Examples include boron trihalides and organoboranes. No hydrogen in them. What Greg is describing is a sub category of acids called Arrhenius acid is a substance that, when added to water, increases the concentration of H+ ions in the water. A Brønsted-Lowry acid (or simply Brønsted acid) is a species that donates a proton to a Brønsted-Lowry base.