| Why Noble? |
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From all the metals and alloys in the earth, there are some that are highly appreciated. They are so called noble metals and include gold, platinum and silver. What makes them noble? There are several qualities that make them most precious. First, they are relatively rare. In parts per billion of the earth's crust, gold constitutes only 3.1, platinum 37 and silver 80. Second, they are quite strong and heavy due to their close-packed atomic structure. Their unique atomic structure is also responsible for their famous lustre, their capacity to conduct heat and electricity, as well as their malleability, the third quality that separates them from the other metals. Malleability is important for two reasons. First, it protects them from the destructive atmospheric forces, and second, it makes it easy for the metal smiths to work with the metals in different ways. The fourth and most important quality is their chemical resistance to oxidation and to corrosion caused of moisture and most acids or alkalis. The only exception is the tarnish of silver that is caused of sulphur, hydrogen sulphide or ozone. But even this tarnish can be removed by applying an alkaline solution on the surface. 
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