The symbol for gold on the periodic table is ‘Au’.
•The discoverer of gold is unknown.
•Although it is believed to have been discovered around
3000BC.
•This precious metal has been highly sought after for many
centuries.
•Gold has the appearance of
•It is soft, dense, shiny and the most malleable and ductile of
all metals known.
•Gold occurs as small nuggets or small grains which can be
found in rocks.
•Melting point: 1063 degrees Celsius
•Boiling point: 2856 degrees Celsius
•Density: 19.3 g cm-3
•Gold isn’t very reactive.
•However, the look of its surface can be changed by
chlorine, fluorine and cyanide.
•Mercury can dissolve Gold, but it doesn’t react with it.
•Coinage
•Jewellery
•Dental Work
•Plating
•Reflectors.
•It is a good conductor of heat and electricity, and because
it doesn’t tarnish when exposed to air gold can be used to
make electrical conductors and printed circuit boards.
•Gold is also used to help shield spacecraft and
skyscrapers from the sun’s heat because it is good at
reflecting infrared radiation.
Gold-198 is a radioactive isotope of gold. It is used for
treating cancer.
Gold sodium thiosulfate (AuNa3O6S4) is used for the
treatment of arthritis.
Chlorauric acid (HAuCl4) is used to preserve photographs by
replacing the silver atoms present in an image.
Pure gold is referred to as ‘24 carat’ gold. It is often alloyed
with silver and copper.
24 carat - 100% gold.
18 carat - 75% gold + 25% silver and/or copper.
9 carat - 37.5% gold + 62.5% silver and/or copper.
Major Steps in Extraction of Gold from its ore.
Host rock and
specks of gold.
Froth Flotation Concentrated
gold ore.
Au
Add zinc or electrolysis
Cyanide process
Au(CN)2- (aq)
Extraction of Gold using Cyanide
4Au (s) + 8CN- (aq) + 2H2O (l) + O2 (g)
4Au(CN)2- (aq) + 4OH- (aq)
The Au(CN)2- is separated from the pulp using activated carbon.
The gold is then recovered by adding zinc (metal ion displacement)
or by electrolysis.
•The most famous piece of gold is the face mask to the boy
king of Egypt, Tutankhamun. Some of the greatest treasures of
goldsmiths art was also found in his tomb.
The properties of gold give it the ability to be beaten into
sheets no thicker than 0.00001 mm or 400 times thinner
than a human hair.
Or
The fact that gold is so malleable and ductile one gram of it
can be beaten into a one square metre sheet.
•In every ton of seawater 1 milligram of gold has been
dissolved, but at the moment it currently costs more to
extract the gold from this than what the gold is worth
itself.
•There is about 120,000 to 140,000 tonnes of gold above
ground.
•Imagine a solid gold cube about the size of a tennis
court. This is the amount of of gold that has been
produced.
•If this amount of was distributed to every person in the
world, you would have only about 23 grams of gold.
Since prehistoric times, gold has been known about and highly
valued.
Gold is used to symbolise purity, value and royalty. It is also a
sign of wealth.
Gold can be found freely in nature, however it is usually found
in silver, quartz, lead, zinc or copper.