Physics and Chemistry
Which elements are the “noble metals”?
Elements 113 through 118 are unstable and have not been confirmed independently by researchers. The names for elements 113 through 118 are under review by the International Union of Pure and Applied Chemistry.
The noble metals are gold (Au, element 79), silver (Ag, element 47), mercury (Hg, element 80), and the platinum group, which includes platinum (Pt, element 78), palladium (Pd, element 46), iridium (Ir, element 77), rhodium (Rh, element 45), ruthenium (Ru, element 44), and osmium (Os, element 76). The term refers to those metals highly resistant to chemical reaction or oxidation (resistant to corrosion) and is contrasted to “base” metals, which are not so resistant. The term has its origins in ancient alchemy whose goals of transformation and perfection were pursued through the different properties of metals and chemicals. The term is not synonymous with “precious metals,” although a metal, like platinum, may be both.
The platinum group metals have a variety of uses. In the United States more than 95 percent of all platinum group metals are used for industrial purposes. While platinum is a coveted material for jewelry making, it is also used in the catalytic converters of automobiles to control exhaust emissions, as are rhodium and palladium. Rhodium can also be alloyed with platinum and palladium for use in furnace windings, thermocouple elements, and in aircraft spark-plug electrodes. Osmium is used in the manufacture of pharmaceuticals and in alloys for instrument pivots and long-life phonograph needles.