So, the Olympic medals are made
of gold, silver and bronze right? Wrong! Pure gold medals would cost an awful
lot, so what are the medals really made from?
The graphic below looks at the
different metals used.
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| Graphic: Compound Interest |
So, what of real gold? Let’s find
out more:
Gold is a chemical element with
the symbol Au (from Latin: aurum) and the atomic number 79. In its purest form,
it is a bright, slightly reddish yellow, dense, soft, malleable and ductile
metal. Chemically, gold is a transition metal and a group 11 element. It is one
of the least reactive chemical elements, and is solid under standard
conditions. The metal therefore occurs often in free elemental (native) form,
as nuggets or grains, in rocks, in veins and in alluvial deposits. It occurs in
a solid solution series with the native element silver (as electrum) and also
naturally alloyed with copper and palladium. Less commonly, it occurs in
minerals as gold compounds, often with tellurium (gold tellurides).
Gold's atomic number of 79 makes
it one of the higher atomic number elements that occur naturally in the
universe. It is thought to have been produced in supernova nucleosynthesis and
from the collision of neutron stars and to have been present in the dust from
which the Solar System formed. Because the Earth was molten when it was just
formed, almost all of the gold present in the early Earth probably sank into
the planetary core. Therefore, most of the gold that is present today in the
Earth's crust and mantle is thought to have been delivered to Earth later, by
asteroid impacts during the Late Heavy Bombardment, about 4 billion years ago.
Gold resists attack by individual
acids, but aqua regia (literally "royal water", a mixture of nitric
acid and hydrochloric acid) can dissolve it. The acid mixture causes the
formation of a soluble tetrachloroaurate anion. It is insoluble in nitric acid,
which dissolves silver and base metals, a property that has long been used to
refine gold and to confirm the presence of gold in metallic objects, giving
rise to the term acid test. Gold also dissolves in alkaline solutions of
cyanide, which are used in mining and electroplating. Gold dissolves in
mercury, forming amalgam alloys, but this is not a chemical reaction.
Gold is a precious metal used for
coinage, jewellery, and other arts throughout recorded history. In the past, a
gold standard was often implemented as a monetary policy within and between
nations, but gold coins ceased to be minted as a circulating currency in the
1930s, and the world gold standard was abandoned for a fiat currency system
after 1976. The historical value of gold was rooted in its relative rarity,
easy handling and minting, easy smelting and fabrication, resistance to
corrosion and other chemical reactions (nobility), and distinctive colour.
The world consumption of new gold
produced is about 50% in jewellery, 40% in investments, and 10% in industry.
Gold's high malleability, ductility, resistance to corrosion and most other
chemical reactions, and conductivity of electricity have led to its continued
use in corrosion resistant electrical connectors in all types of computerized
devices (its chief industrial use). Gold is also used in infrared shielding,
coloured glass production, gold leafing, and tooth restoration. Certain gold
salts are still used as anti-inflammatories in medicine.
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