Using this definition for noble metals then, we will find that silver is less noble than, say, graphite (although graphite is an elemental form of carbon and, therefore, is not considered a metal). Below is a comparison of the chemical nobility of the precious metals (again, excluding rhenium), with details of their specific electronic configurations, simplified reactions (as per the pH diagram), and electrode potentials. Occurring in nature in metallic form, these two precious metals can be produced sans the use of extraction metallurgy. These other characteristics of gold and silver make them both well suited for coinage: They are not radioactive. They are more ductile or softer than most other elements. They are less reactive compared with other elements. The authorities, however, will have undertaken a fixed exchange rate with a country that's on the gold standard. Before the turn of the 20th century, countries that were still on silver standard started pegging their monetary units to the gold standard of either the United States or the United Kingdom. Gold As An Investment: Ways Of Investing In Gold Four of the nine known precious metals are regarded as investment commodities. Of these four, gold is the most popular. Investing in gold is a way of protecting against crises that may be brought about by economic or political instability or by social unrest. mol-1 Heat of Vaporization: 563 kJ.mol-1 Atomic: Oxidation States: -3, -1, 0, 1, 2, 3, 4, 5, 6 Electronegativity: 2.20 (Pauling scale) Atomic Radius: 136 picometre Covalent Radius: 141 6 picometre Because of its characteristic of being very brittle, pure iridium is quite difficult - almost impossible, in fact - to machine. Half ounce coin (0.55 troy ounce in weight, 2.22 millimeters thick, and 27.07 millimeters in diameter). 4. One ounce coin (1.09 troy ounces in weight, 2.84 millimeters thick, and 32.77 millimeters in diameter). Each of these four coin varieties is 22K, containing 91.67% pure gold and 8.33% copper. This composition was meant to make the coins more durable and harder and thus resist dents and scratches, as, again, they were originally intended for circulation.