A helpful tool for predicting acid and base strength is the periodic table. By understanding the trends among the elements listedthere, you can predict the relative acid and base strengths of the various functional groups. Also, you can predict the direction of a particular reaction and the stability of the products. Consider the relative acid strengths of the Brønsted-Lowry
hydrogen halide acids, HF, HCl, HBr, and HI. These four compounds differ only in the halogen bonded to the hydrogen. Their general ionization equation is: