![]() ![]() 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. ![]() The oxidation state of any chemically bonded carbon may be assigned by adding -1 for each bond to more electropositive atom (H, Na, Ca, B) and +1 for each bond to more electronegative atom (O, Cl, N, P), and 0 for each carbon atom bonded directly to the carbon of interest.A vertical column in the periodic table.The algebraic sum of the oxidation states in an ion is equal to the charge on the ion.Īssigning oxidation numbers to organic compounds.The algebraic sum of the oxidation numbers of elements in a compound is zero.Hydrogen has an oxidation number of +1 when combined with non-metals, but it has an oxidation number of -1 when combined with metals.Oxygen almost always has an oxidation number of -2, except in peroxides (H 2O 2) where it is -1 and in compounds with fluorine (OF 2) where it is +2.The alkaline earth metals (group II) are always assigned an oxidation number of +2.The alkali metals (group I) always have an oxidation number of +1.Fluorine in compounds is always assigned an oxidation number of -1.The oxidation number of a monatomic ion equals the charge of the ion.The oxidation number of a free element is always 0.You can find examples of usage on the Divide the redox reaction into two half-reactions page. ![]() Since the electrons between two carbon atoms are evenly spread, the R group does not change the oxidation number of the carbon atom it's attached to. Unlike radicals in organic molecules, R cannot be hydrogen. Organic compounds can be written in such a way that anything that doesn't change before the first C-C bond is replaced with the abbreviation R (Figure 1c). When dealing with organic compounds and formulas with multiple atoms of the same element, it's easier to work with molecular formulas and average oxidation numbers (Figure 1d). Notice that changing the CH 3 group with R does not change the oxidation number of the central atom. ![]() R is an abbreviation for any group in which a carbon atom is attached to the rest of the molecule by a C-C bond. Different ways of displaying oxidation numbers of ethanol and acetic acid. ![]()
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