gustiness in atmospheric chemistry, 648 Haber–Weiss reaction, 648 haem, 649 halato-telechelic polymer, 649 half life, , 649 half life of a radionuclide , 650 half thickness in radiochemistry, 650 half-chair, 650 half-life, , of a transient entity , 650 half-life, , of a photochromic system , 651 half-peak potential, 651 half-wave potential, 651 half-width of a band , 651 halirenium ions, 652 halochromism, 652 haloforms, 652 halohydrins, 652 halonium ions, 653 halophiles, 653 hamiltonian operator , 653 Hammett equation (Hammett relation), 653 Hammond principle (Hammond postulate), 654 Hammond–Herkstroeter plot, 654 handedness, 655