As stated previously, the reactivity of Arrhenius acids and bases is limited, but predictable. However, in order to recognize Arrhenius reactants and, subsequently, predict the products that are generated when these substances participate in chemical reactions, chemical formula patterns for writing or identifying the formulas of Arrhenius acids and bases must first be developed and applied.
Recall that Arrhenius prepared aqueous solutions so that he could study the ionizations of strong and weak electrolytes, which dissociate, or separate, into cations and anions when dissolved in water. During his investigations, Arrhenius observed that hydrogen ions, H+1, which are also known as "protons," were generated upon the hydration and subsequent dissociation of an unexpectedly-high number of electrolytes. Due to the frequency with which these charged particles were detected in the aqueous solutions that he prepared, Arrhenius regarded the production of H+1 ions as a chemically-significant phenomenon and classified the electrolytes from which these particles were generated as "acids." However, since, as stated above, strong and weak electrolytes must generate both cations and anions when dissolved in a solvent, an Arrhenius acid must, by definition, contain hydrogen, which ionizes to form a proton, and a component that ionizes to produce a stable, negatively-charged particle.
Finally, because all Arrhenius acids contain hydrogen, the chemical formula and name of a specific Arrhenius acid is dependent on the type of anion that it contains. Monatomic, or single-atom, anions are generated when non-metals gain electrons to achieve octet configurations. Anions can also be polyatomic, or multi-atom, units that bond as indivisible charged entities and have defined formulas, names, and charges. The patterns for determining the chemical formulas and names of Arrhenius acids that contain monatomic and polyatomic anions will be presented and applied in the following two sections of this chapter.