Period 5 element and because of its rarity, rhodium is usually alloyed with platinum or palladium and applied in high-temperature and corrosion-resistive coatings. White gold is often plated with a thin rhodium layer to improve its optical impression while sterling silver is often rhodium plated for tarnish resistance. Rhodium detectors are used in nuclear reactors to measure the neutron flux level. Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named
Group 3 element the current heaviest element known, oganesson. In 1787, Swedish part-time chemist Carl Axel Arrhenius found a heavy black rock near the Swedish village of Ytterby, Sweden (part of the Stockholm Archipelago). Thinking that it was an unknown mineral containing the newly discovered element tungsten, he named it ytterbite. Finnish scientist Johan Gadolin identified a new oxide or "earth" in Arrhenius' sample in 1789, and published his completed analysis in 1794; in 1797, the new oxide was named "yttria". In the decades after French scientist Antoine Lavoisier developed the first modern definition of chemical elements, it was believed that earths could