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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 ...
A Assuming an altitude of 194 metres above mean sea level (the worldwide median altitude of human habitation), an indoor temperature of 23 °C, a dewpoint of 9 °C (40.85% relative humidity), and 760 mmHg sea level–corrected barometric pressure (molar water vapor content = 1.16%). B Calculated values *Derived data by calculation.
Values are in kelvin K and degrees Celsius °C, rounded For the equivalent in degrees Fahrenheit °F, see: Boiling points of the elements (data page) Some values are predictions
85 At astatine; WEL: 575 K: ... unless noted. Triple point temperature values (marked "tp") are not valid at standard pressure. ... A.M. James and M.P. Lord in ...
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°).
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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