When Svante Arrhenius first proposed his acid base theory, he was a doctoral candidate. His professors thought his ideas were unfounded. Within a decade, the Arrhenius theory of acid base was widely accepted and praised within the scientific world. Arrhenius defined acids as compounds having an ionizable hydrogen and bases as compounds with ionizable hydroxides. Eventually scientists adopted a broader theory which includes more compounds to define acids and bases. The Bronsted-Lowry acid base theory defines an acid as a and a base as a .