When in 1840, Henry Talbot discovered an additional chemical twist, that is so called latent silver image, that had been briefly exposed onto a layer of silver iodide could be revealed using gallic acid, the effect was seen as magical, a devilish art. A photon of light hitting the negative nitrate anion frees an electron, which ultimately combines with the positive silver ions to make neutral silver metal, darkening the surface of the material. This reaction, the dawn of photography, was all thanks to the fact that silver salts are sensitive to light. He used stencils to produce black images with the paste. In 1727, a German physicist called Johann Heinrich Schulze found that a paste of chalk and silver nitrate salt was blackened by light. But the same chemical properties that tarnished its image let it to make another mark in history, by allowing history itself to be recorded in the photograph. So it's a high maintenance element another reason why it has always been outshone by gold. The metal reacts with sulphur in the air, rapidly forming a dull, dark silver sulphide tarnish that has to be polished off. But a gleaming collection of silverware isn't easy to maintain. It's a soft and pliable metal with a relatively low melting point and that means it can be hammered and moulded into shape, so the same metal that was used to make money that was gradually outdated could also be transformed into vases, platters, cutlery and goblets tableware that has created displays of household wealth through the centuries. These coins actually form the basis for the economies of some ancient Mediterranean civilizations. It's not just rare or precious, as its more expensive cousin, gold, but there is evidence from as early as 3000 BC that humans extracted silver from naturally occurring silver sulphide deposits in rocks to make coins and jewellery. Its lustre shine has been coveted since ancient times. Political stability of top reserve holderĪ percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators. The higher the value, the larger risk there is to supply.Ī percentile rank for the political stability of the top producing country, derived from World Bank governance indicators. The percentage of the world reserves located in the country with the largest reserves. The higher the value, the larger risk there is to supply. The percentage of an element produced in the top producing country. Low = substitution is possible with little or no economic and/or performance impact Medium = substitution is possible but there may be an economic and/or performance impact
High = substitution not possible or very difficult. 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.
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