General: Chemical Symbol: Pd Atomic Number: 46 Category (as an element): Transition Metal Group/ Period/ Block (in the Periodic Table): 10/ 5/ d Atomic Weight: 106.42 g.mol-1 Electron Configuration: [Kr] 4d10 Physical: Density (near room temperature): 12.023 g.cm-3 Liquid Density (at melting point): 10.38 g. Distribution of these were as follows: electrochemical uses (1,100 kilograms); electrical uses (780 kilograms); for catalysis (750 kilograms); and other applications (1,100 kilograms). Iridium is found at highest concentrations within the Earth's crust in three specific types of geologic structures: in impact craters, in igneous deposits, and in deposits reworked from either of the first two. Platinum: Most Widely Traded Of The Platinum Group Metals In the periodic table of the chemical elements, six metallic elements - all transition metals - are clustered together and lie in the d-block (the d-block in the periodic table refers to groups 8, 9, and 10, periods 5 and 6). These six elements are collectively referred to as the platinum group metals. This precious metal, which belongs to the platinum group metals, is rhodium. With its current price of around 1,000 U.S. dollars per troy ounce, rhodium is about five times costlier than platinum. Wollaston's discovery of rhodium was made possible with the use of crude platinum ore. He first dissolved the ore in nitro-hydrochloric acid (also called aqua regia) and neutralized the acid with lye (or sodium hydroxide). Nuggets that have very rich deep orange/yellow color are sure to have higher gold content than pale ones. Also, there is a system called "millesimal fineness" which is used to denote the purity of gold alloy (also of silver and platinum alloys) by parts per thousand of pure metal by mass in the alloy. The ranking appears different when the estimated world market prices, per troy ounce, of these nine precious metals are considered (estimates as of January 2010): 1st: Rhodium - USD2,750 2nd: Platinum - USD1,555 3rd: Gold - USD1,131 4th: Palladium - USD424 5th: Iridium - USD408 6th: Osmium - USD380 7th: Rhenium - USD194 8th: Ruthenium - USD173 9th: Silver - USD18 Of the nine precious metals, gold and silver are the best known.