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 5 element he retracted his claim. Niobium was discovered by the English chemist Charles Hatchett in 1801. Tantalum was first discovered in 1802 by Anders Gustav Ekeberg. However, it was thought to be identical to niobium until 1846, when Heinrich Rose proved that the two elements were different. Pure tantalum was not produced until 1903. Dubnium was first produced in 1968 at the Joint Institute for Nuclear Research by bombarding americium-243 with neon-22. Dubnium was again produced at the Lawrence Berkeley Laboratory in 1970. The names "neilsbohrium" and "joliotium" were proposed for the element, but in 1997, the IUPAC decided to name