![]() ![]() Each element is identified by the number of protons in its atoms.There are 118 elements on the periodic table.Its use in electronic circuitry is cost-effective due to its reliability. A small quantity of gold is found in almost every electronic device from cell phones to GPS units to computers. Gold doesn’t corrode, it’s an excellent conductor of electricity and its malleability means it is easy to work with. The word aurum is derived from an even earlier word that means ‘glow’. The chemical symbol for gold is Au – from ‘aurum’, the Latin word for gold. The troy ounce (31.10 g) is heavier than a standard ounce (28.35 g). Gold is still traded in troy ounces – a unit that dates back to the Middle Ages. The word ‘carat’ comes from the word ‘carob’ – the seed that was used to balance the scales in ancient Asian markets. Alloys of gold include 18-ct (18 parts gold and 6 parts other metals), 12-ct (12 parts gold and 12 parts other metals) and so on. Gold is measured with a carat (ct) rating – the purest form of elemental gold is 24-ct. We tend to measure and weigh gold with fairly old methods too. Evidence shows an association between humans and gold dating back to 40,000 BC. Gold is thought to be the first recorded metal worked by humans. Gold is the only truly yellow metal found on Earth, and it can be found in its pure elemental form. Alluvial gold – like that found in Otago and the West Coast – has been eroded from the rocks and can be found as small flakes or larger nuggets in river gravel. Gold and silver-bearing rock has to be crushed and chemically treated to get the precious element. Examples of this are found on the Coromandel Peninsula. Hot fluid can pick up gold as it flows through fractures in the Earth, leaving very tiny particles embedded in quartz veins. ![]() ![]() It suggests that tectonic plate movements allowed metal-rich fluids to come through very deep cracks and form gold deposits near the Earth’s surface. A second hypothesis has recently come to light. One idea is that the gold present in Earth’s crust and mantle came from meteors nearly 4 billion years ago when billions of tonnes of space rocks landed on Earth. However, the Earth was a molten liquid when it formed, so heavy elements like gold likely sank into the core. Scientists believe that gold dust was present when the Solar System was formed. They think that gold dust is produced when neutron stars collide, but ideas differ about why we find it in Earth’s crust and mantle. Scientists are not certain about the origin of the Earth’s gold deposits. Gold’s cosmic origins (and those closer to home) The noble metals are all found close to one another in the periodic table of elements. ![]() The noble metals resist oxidation and corrosion in humid air, which is why they are often used in coinage and jewellery. Gold is a noble metal along with silver, platinum, palladium and a few others. Imagine stretching even the chewiest piece of gum into 1 square metre! For reference, a stick of gum weighs about 1 gram. Gold is the most malleable of all metals – 1 gram of gold can be hammered into a 1 square metre sheet of gold foil. Its official chemical symbol is Au, and its atomic number is 79, which means that a gold molecule has 79 protons in its nucleus. Gold is a chemical element – a substance that contains only one type of atom. ![]()
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