The Science of Alloys: Understanding 18-Karat Gold
The Atomic Number of Gold: What Does 79 Mean
Gold as money and the gold standard
Modern Uses of Gold in Technology and Industry
Alloys are a combination of metals with other metals and elements. Gold is a malleable metal - it is ductile, and 28.34-gram gold wire can be drawn into 80 km of thin gold wire of 5 microns diameter. The symbol of gold is Au and its atomic number is 79. Each gold atom has 79 protons in its nucleus. The atomic mass of a gold atom is 196.967 and its radius is 0.1442 nm. Gold is used to make electrical contacts, jewellery and bonding wires.
A metal alloy is a substance that combines more than one metal or it is a mix of a metal and another non-metallic element. For example, brass is an alloy of copper and zinc and steel is an alloy of iron and carbon. Alloys contain atoms of different sizes and how the atoms combine and interact with one another gives the alloy their classification. In alloy chemistry, an alloy is classified according to its atomic arrangement as -
It is an alloy formed from atom exchange mechanisms. The metallic components of substitutional alloys have similar atomic radii and chemical-bonding capabilities. Thus, the atoms from one metal can occupy the same sites as their counterpart in the atomic metal lattice. Some examples of substitutional alloys are brass and bronze.
It is formed when smaller atoms from an element fill the holes of the metal lattice. The atoms from each element do not occupy the same sites in the metal lattice. An instance of interstitial alloy is Steel, in which smaller carbon atoms fill spaces between iron atoms.
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18 Carat gold comprises 75% gold and 25% other metals. 18-carat gold is a substitutional alloy in which generally copper or silver is used to strengthen the gold. It is the choice of gold alloy for jewellery as it can be moulded into different shapes and yet it is sturdy enough to withstand the wear and tear that comes from daily use.
Young’s Modulus of Material elasticity is related to rigidity and is defined as a ratio between applied stress and the elastic strain that it produces. The number of protons in a gold nucleus is fixed at 79, however, the number of neutrons can vary from one atom to another. This property gives the metal several isotopes and it is the only stable non-radioactive isotope.
The yellow colour of gold is related to the arrangement of the outer electrons around the gold nucleus. It is caused by the transition of electrons between energy bands and conditions of intense light absorption at different wavelengths that are necessary to produce the typical gold colour are fulfilled by the transition from the d band to unoccupied positions in the conduction band.
As per the National Mining Association, the first known history of gold is in modern-day Eastern Europe in 4000 BC as decorative objects. Ancient Greek texts, the Iliad and Odyssey mention gold as the glory of the immortals and a sign of wealth among ordinary humans. The “Gold of Troy” treasure hoard that was excavated in Turkey, dates to the era 2450 -2600 B.C. It shows the range of gold-work from delicate jewellery to a gold gravy boat that weighs a full troy pound. History is dotted with incidents of the Phoenicians, Egyptians, Indians, Hittites, Chinese, and others who were sent to work the mines, as prisoners of war, slaves and criminals.
In 1500 BC, in the ancient empire of Egypt, the gold-bearing region Nubia made the medal its first official medium of exchange in international trade. It created the coin Shekel which weighed 11.3 grams and became the standard unit of measure in the Middle East.
In modern times, the gold standard emerged as a monetary system in which the currency was valued against a fixed quantity of gold. For instance, GB Pound 1 could be exchanged for gold of a certain quantity from the Bank. Around World War I, the gold standard was abandoned by many countries for fiat money.
Source: Use of Gold
Gold has many special properties that make it useful as a conductor of electricity, and its malleable properties make it easy to work with - stretched into wire or hammered into thin sheets, or as an alloy with other metals to be melted and cast into detailed shapes. It is prominently used in jewellery, wedding ornaments, Olympic medals, Oscars, Grammys, crucifixes and ecclesiastical art.
Though we have turned to fiat money for transactions, gold bullion in bricks, ingots and biscuits is still used as savings instruments by central banks, investment companies, and individuals. It is a form of diversifying one’s investment and protecting one’s assets against inflation.
Gold is highly efficient for carrying tiny amounts of electricity and is used in connectors, soldered joints, switch and relay contacts, connecting wires and connection strips. It is also used in phones, global positioning system (GPS) units, desktops, laptops, calculators, personal digital assistants, and other small electronic devices.
Gold is also used in medical, aerospace, and glass-making fields.
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