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Astatine-218 was the first astatine isotope discovered in nature. [113] Astatine-219, with a half-life of 56 seconds, is the longest lived of the naturally occurring isotopes. [6] Isotopes of astatine are sometimes not listed as naturally occurring because of misconceptions [103] that there are no such isotopes, [114] or discrepancies in the ...
Astatine has 23 nuclear isomers (nuclei with one or more nucleons – protons or neutrons – in an excited state). A nuclear isomer may also be called a "meta-state"; this means the system has more internal energy than the "ground state" (the state with the lowest possible internal energy), making the former likely to decay into the latter ...
Its predicted melting and boiling points are 52±15 °C and 177±10 °C respectively, so that it is probably neither noble nor a gas; it is expected to have a density of about 6.6–7.4 g/cm 3 around room temperature. It is expected to have a barely positive electron affinity (estimated as 5 kJ/mol) and a moderate ionisation energy of about 860 ...
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Astatine monochloride [7] (AtCl) is made either by the direct combination of gas-phase astatine with chlorine or by the sequential addition of astatine and dichromate ion to an acidic chloride solution. Iodine monobromide (IBr) is made by the direct combination of the elements to form a dark red crystalline solid. It melts at 42 °C and boils ...
The standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions.A degree sign (°) or a superscript Plimsoll symbol (⦵) is used to designate a thermodynamic quantity in the standard state, such as change in enthalpy (ΔH°), change in entropy (ΔS°), or change in Gibbs free energy (ΔG°).
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
Astatine is known to react with its lighter homologs iodine, bromine, and chlorine in the vapor state; these reactions produce diatomic interhalogen compounds with formulas AtI, AtBr, and AtCl. [4] The first two compounds may also be produced in water – astatine reacts with iodine/ iodide solution to form AtI, whereas AtBr requires (aside ...