The gold particles, having higher density than the other materials (examples, mud, sand and gravel; also, gold is about nineteen times heavier than water), settle to the bottom of the pan, while the lighter materials are washed over the side. Sluice Box: This method uses the same principle as that in gold panning, only on a larger scale. cm-3 Liquid Density (at melting point): 9.320 g.cm-3 Melting Point: 961.78 C, 1234.93 F, 2041.4 K Boiling Point: 2162 C, 3924 F, 2435 K Heat of Fusion: 11.28 kJ.mol-1 Heat of Vaporization: 250.58 kJ.mol-1 Atomic: Oxidation States: 1, 2, 3 Electronegativity: 1.93 (Pauling scale) Atomic Radius: 144 picometre Covalent Radius: 145 5 picometre Van der Waals Radius: 172 picometre Ionization Energies: 731 kJ. Its occurrence is similar to that of ruthenium, and its primary use is as a catalytic converter. Rhodium is considered perhaps the rarest element. It is also known to be the most expensive precious metal, with a price estimated to be about USD2,750 per troy ounce (USD88,415 per kilogram) as of January 2010. In fact, this precious metal has been regarded as a form of currency and a store of value for over four centuries. There are different ways by which one may invest in silver. Six are presented here: Buying silver coins: This is a popular way of taking hold of silver - physically. Perhaps the best example of a silver coin is the Canadian Silver Maple Leaf, which consists of 99.99% pure silver. mol-1 Electron Configuration: [Xe] 4f14 5d10 6s1 Physical: Density (near room temperature): 19.30 g.cm-3 Liquid Density (at melting point): 17.31 g.cm-3 Melting Point: 1064.18 C, 1947.52 F, 1337.33 K Boiling Point: 2856 C, 5173 F, 3129 K Heat of Fusion: 12.55 kJ.mol-1 Heat of Vaporization: 324 kJ.mol-1 Atomic: Oxidation States: -1, 1, 2, 3, 4, 5 Electronegativity: 2.54 (Pauling scale) Atomic Radius: 144 picometre Covalent Radius: 136 6 picometre Van der Waals Radius: 166 picometre Ionization Energies: 890.1 kJ. Owning a gold certificate: A gold investor may opt to hold on to a gold certificate rather than store the physical gold bullion. The gold certificate allows the investor to buy and sell the security and do away with the many difficulties associated with the actual gold's transfer. Trading in Gold Exchange-Traded Funds (GETFs): Trading in GETFs is like trading shares in, say, the New York Stock Exchange or the London Stock Exchange.