Died #OTD in 1989. Emilio Segrè was an Italian and naturalized-American physicist who discovered the elements technetium and astatine, & the antiproton, a subatomic antiparticle, for which he was awarded the Nobel Prize in Physics in 1959 along with Owen Chamberlain.
Together with Glenn T. Seaborg, he discovered technetium-99m—the first artificially produced element (1937). Tc99m is first element found to have no stable isotopes, filling a missing spot on the periodic table.