Editing Radon (section)

=== Physical properties ===
[[File:Radon decay in a cloud chamber.jpg|thumb|Radon in a cloud chamber showing its radiation]]
Radon is a colorless, odorless, and tasteless<ref name="guide">{{cite web |date=2016 |title=A Citizen's Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon |url=https://www.epa.gov/radon/citizens-guide-radon-guide-protecting-yourself-and-your-family-radon |publisher=Environmental Protection Agency}}</ref> gas and therefore is not detectable by human senses alone. At [[standard temperature and pressure]], it forms a [[monatomic gas]] with a density of 9.73&nbsp;kg/m<sup>3</sup>, about 8 times the density of the [[Atmosphere of Earth|Earth's atmosphere]] at sea level, 1.217&nbsp;kg/m<sup>3</sup>.<ref>{{cite web |last=Williams |first=David R. |date=2007-04-19 |title=Earth Fact Sheet |publisher=[[NASA]] |url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html |access-date=2008-06-26}}</ref> It is one of the densest gases at room temperature (a few are denser, e.g. [[perfluorobutane|CF<sub>3</sub>(CF<sub>2</sub>)<sub>2</sub>CF<sub>3</sub>]] and [[tungsten hexafluoride|WF<sub>6</sub>]]) and is the densest of the noble gases. Although colorless at standard temperature and pressure, when cooled below its [[freezing point]] of {{convert|202|K}}, it emits a brilliant [[radioluminescence]] that turns from yellow to orange-red as the temperature lowers.<ref>{{cite web |title=The Element Radon|website = It's Elemental |url=http://education.jlab.org/itselemental/ele086.html |access-date= |publisher=Jefferson Lab}}</ref> Upon [[condensation]], it glows because of the intense radiation it produces.<ref>{{cite book |last=Thomas |first=Jens |date= 2002 |title= Noble Gases |publisher=Marshall Cavendish |isbn=978-0-7614-1462-9 |page=13 |url=https://books.google.com/books?id=T0Iiv0BJ1E0C&pg=PA13}}</ref> It is sparingly [[soluble]] in water, but more soluble than lighter noble gases. It is appreciably more soluble in [[organic liquid]]s than in water. Its solubility equation is as follows:<ref>{{Unbulleted list citebundle|{{cite book |last1=Gerrard |first1=W |title=Solubility Data Series |date=1979 |publisher=Pergamon Press |pages=264–271 |edition=Vol.2 |url= https://iupac.github.io/SolubilityDataSeries/volumes/SDS-2.pdf }}|{{cite book |last1=Battino |first1=R |title=Solubility Data Series |date=1979 |publisher= Pergamon Press |pages=227–234 |edition=Vol.2 |url=https://iupac.github.io/SolubilityDataSeries/volumes/SDS-2.pdf }}|{{cite journal |last1=Saito |first1=M |title=''Determination of Radon Solubilities to 1,2-Dimethylbenzene, 1,3- Dimethylbenzene, 1,4-Dime thylbenzene, 1,3,5-Trimethylbenzene, 1, 2,4-Trimethylbenzene and 1-Isopropyl-4-methylbenzene'' |journal=Nippon Kagaku Kaishi |date=1999 |issue=6 |pages=363–368|doi=10.1246/nikkashi.1999.363 |url=https://www.jstage.jst.go.jp/article/nikkashi1972/1999/6/1999_6_363/_article/download/-char/ja|doi-access=free }}}}</ref>

: <math>\chi = \exp(B/T-A)</math>

where <math>\chi</math> is the molar fraction of radon, <math>T</math> is the absolute temperature, and <math>A</math> and <math>B</math> are solvent constants.