But while platinum is generally resistant to corrosion, it is corroded by certain elements, such as cyanides (potassium cyanide or sodium cyanide), caustic alkalis, sulfur, and any of the five halogens (astatine, bromine, chlorine, fluorine, and iodine). The following lists some of the properties of platinum: General: * Chemical Symbol: Pt * Atomic Number: 78 * Category (as an element): Transition Metal * Group/ Period/ Block (in the Periodic Table): 10/ 6/ d * Atomic Weight: 195.084 g. In terms of mass abundance, expressed in parts per billion (ppb), here's how the nine precious metals are ranked (rare to rarest): 9th: silver (75 ppb); 8th: palladium (15 ppb); 7th: gold (4 ppb); 6th: osmium (1.5 ppb); 5th to 3rd: iridium, rhodium, and ruthenium (1 ppb); 2nd: rhenium (0.7 ppb); and 1st: platinum (0.003 ppb). As electrical contact materials, due to its high resistance to arc corrosion and wear. 4. As catalysts for hydrogenation of fine chemicals, because of its high resistance to chemical poisoning from phosphorus, sulfur, and nitrogen. 5. As treatment for liver cancer, because of its radioactive isotopes. To put it another way, bullion is valued based on the mass and purity of the metal used, instead of its artificial currency value. New sources of ore have been discovered and there also have been improvements in the mining and refining processes. These two factors may cause the values of gold, silver, and the other precious metals to diminish. mol-1 Atomic: Oxidation States: 6, 5, 4, 3, 2, 1, -1 Electronegativity: 2.28 (Pauling scale) Atomic Radius: 134 picometre Covalent Radius: 142 7 picometre Ionization Energies: 719.7 kJ.mol-1 (first), 1740 kJ.mol-1 (second), 2997 kJ.mol-1 (third) The principal use of rhodium is as a catalytic converter in automotive vehicles, which reduces the toxicity of engine emissions by converting these into less harmful gases. Also called fire assay, the method involves treating ores or alloyed metals under high temperatures and carefully controlled operations to separate gold from base metals (copper, zinc, or lead), which may be present in the ore. Once the base metals are heated at high temperatures, the gold (as well as the other precious metals that may be present) remains apart and the other non-precious metals react forming other compounds.