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.Ĭrustal abundance (ppm) Relative supply riskĪn integrated supply risk index from 1 (very low risk) to 10 (very high risk). 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. IsotopesĪtoms of the same element with different numbers of neutrons.ĬAS number Where more than one isotope exists, the value given is the abundance weighted average. 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 (g cm −3)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.īoiling point The arrangements of electrons above the last (closed shell) noble gas. The number of protons in an atom.Įlectron configuration These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f).Ītomic number The atomic number of each element increases by one, reading from left to right.īlockĮlements are organised into blocks by the orbital type in which the outer electrons are found. PeriodĪ horizontal row in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell. GroupĪ vertical column in the periodic table.

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