What's New In Chemistry?

EXTENDED READING FOR
TOPIC: METALS

Gold has no oxides and is not affected by oxygen in the atmosphere as are other metals. This is why gold does not tarnish -- tarnish is the result of metal reacting with oxygen in a process called oxidation.

Gold is malleable to the point that it can be hammered into a leaf or sheet of foil. Since gold alone is too soft to hold a form, gold is alloyed (combined with other metals) in order to make jewelry.

When gold is alloyed, its ductility is diminished, but its malleability remains constant, except when large percentages of copper are added to the alloy. Nickel used in a white gold alloy has the same characteristics as silver.

Zinc is added to the white gold alloy and lightens the color, but amounts in greater percentage than 14% of the entire alloyed mass will change the color to red and make the alloy brittle. The reason for using zinc in gold alloys is to absorb the oxygen to prevent silver and copper oxides in the mix.

Resource:
"Precious Mineral Marketing Company"
http://www.pmmcghana.com/newheaderpix5.jpg
"Gallery of Unique Wedding Bands & Jewelry"
http://handwovenbands.com/gold.htm