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. That is, similar elements do not have similar atomic weights.A vertical column in the periodic table. This law states that when the elements are listed in order of increasing atomic weights, their properties vary periodically. If a list were made of all elements, we would find the sequence halogen, noble gas, alkali metal, and alkaline-earth metal several more times.ĭmitri Ivanovich Mendeleev proposed the periodic law behind his periodic table compiling. Exactly the same sequence is repeated eight elements later (Ne, Na, and Mg), but this time a halogen (F) precedes the noble gas. The second, third, and forth elements on the list (He, Li, and Be) are a noble gas, an alkali metal, and an alkaline-earth metal, respectively. Obtaining atomic weights, we haveĮlements which belong to families we have already discussed are indicated by shading around their symbols. You can see that such a relationship exist by listing symbols for the first dozen elements in order of increasing relative mass. Therefore it seems reasonable to expect some correlation between this microscopic property and macroscopic chemical behavior. This could account for the related chemical reactivities and analogous compounds of these elements.Īccording to Dalton’s atomic theory, different kinds of atoms may be distinguished by their relative masses (atomic weights). Atoms of sodium ought to be similar in some way to atoms of lithium, potassium, and the other alkali metals. The similarities among macroscopic properties within each of the chemical families lead one to expect microscopic similarities as well. 1950-1999 (+15 elements): Manhattan_Project and Particle physics issues, for atomic numbers 97 and above.1900-1949 (+13 elements): impulse from the old quantum theory, the Refinements to the periodic table, and quantum mechanics.1850-1899 (+23 elements): the age of Classifying Elements received an impulse from the Spectrum analysis.1800-1849 (+22 elements): impulse from Scientific Revolution and Atomic theory and Industrial Revolution.Before 1800 (36 elements): discoveries during and before the Age of Enlightenment.\): Periodic Table showing when each element was discovered
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