![]() The availability of suitable substitutes for a given commodity. A higher recycling rate may reduce risk to supply. The percentage of a commodity which is recycled. The number of atoms of the element per 1 million atoms of the Earth’s crust. This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores. The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems.ĭata for this section been provided by the British Geological Survey.Īn integrated supply risk index from 1 (very low risk) to 10 (very high risk). Where more than one isotope exists, the value given is the abundance weighted average.Ītoms of the same element with different numbers of neutrons. This is approximately the sum of the number of protons and neutrons in the nucleus. The mass of an atom relative to that of carbon-12. The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.ĭensity is the mass of a substance that would fill 1 cm 3 at room temperature. The temperature at which the liquid–gas phase change occurs. The temperature at which the solid–liquid phase change occurs. The arrangements of electrons above the last (closed shell) noble gas. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f). The atomic number of each element increases by one, reading from left to right.Įlements are organised into blocks by the orbital type in which the outer electrons are found. Members of a group typically have similar properties and electron configurations in their outer shell.Ī horizontal row in the periodic table. First introduced in the reign of Emperor Constantine it weighed up to 70 Troy grains and was in currency from the 4th to the 12th centuries CE.A vertical column in the periodic table. One of the most famous gold coins in antiquity was the Roman bezant. ![]() The Mycenaean civilization also widely used gold coins, as did the later Greek and Roman Empires, although silver was the more usual material used. The salt mixed with the silver and formed a vapour of silver chloride leaving behind pure gold which could be used to create a standardised coinage of guaranteed gold content. Even the purest naturally occurring gold can contain 5% silver but the Lydians were able to refine their gold using salt and furnace temperatures of between 600 and 800☌. The first pure gold coins with stamped images are credited to king Croesus of Lydia, 561-546 BCE and a contemporary gold refinery has been excavated at the capital, Sardis. Irregular in shape and often with only one side stamped, the coins were usually made of electrum. Gold was first used as coinage in the late 8th century BCE in Asia Minor. The value and beauty of gold made it an ideal material for particularly important political and religious objects. The Romans used gold as a setting for precious and semi-precious gemstones, a fashion continued into the Byzantine era with the use of pearls, gems and enamels. In South America, gold was similarly worked by the Chavin civilization of Peru around 1200 BCE and gold casting was perfected by the Nazca society from 500 BCE. Techniques and shapes included filigree (a technique known to the Egyptians from 2500 BCE) where the gold is pulled into wire and twisted into different designs), beaten thin shapes, granulation (surface decoration with small, soldered granules of gold), embossing, chasing, inlaying, moulding and engraving. Gold jewellery took the form of necklaces, bracelets, earrings, rings, diadems, pendants, pins and brooches. The Minoan civilization on Crete in the early 2nd millennium BCE is credited with producing the first cable chain jewellery and the Minoans made a vast array of jewellery items using an extensive range of techniques. Gold jewellery was worn by both men and women in the Sumer civilization around 3000 BCE and gold chains were first produced in the city of Ur in 2500 BCE. Electrum (the natural alloy of gold and silver) was used in jewellery by the Egyptians from 5000 BCE. In most ancient cultures gold was popular in jewellery and art because of its value, aesthetic qualities, ductility and malleability.
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