Editing Radium (section)

==Bulk properties==
Radium is the heaviest known [[alkaline earth metal]] and is the only [[radioactive]] member of its group. Its physical and chemical properties most closely resemble its lighter [[congener (chemistry)|congener]], [[barium]].{{sfn|Greenwood|Earnshaw|1997|page=112}}

Pure radium is a [[volatility (chemistry)|volatile]], [[Lustre (mineralogy)|lustrous]] silvery-white metal, even though its lighter congeners [[calcium]], [[strontium]], and barium have a slight yellow tint.{{sfn|Greenwood|Earnshaw|1997|page=112}} Radium's lustrous surface rapidly becomes black upon exposure to air, likely due to the formation of [[radium nitride]] (Ra<sub>3</sub>N<sub>2</sub>).{{sfn|Kirby|Salutsky|1964|page=4}} Its [[melting point]] is either {{convert|700|°C}} or {{convert|960|°C}}{{efn|
Both values are encountered in sources and there is no agreement among scientists as to the true value of the melting point of radium.{{sfn|Kirby|Salutsky|1964|page=4}}
}} and its [[boiling point]] is {{convert|1737|°C}}; however, this is not well established.<ref name="brit">
{{Britannica|489270|Radium|Timothy P. Hanusa}}
</ref> Both of these values are slightly lower than those of barium, confirming [[periodic trend]]s down the group&nbsp;2 elements.<ref name=Lide2004>{{cite book
 |editor1-last = Lide |editor1-first=D.R.
 |display-editors = etal
 |year = 2004
 |title = CRC Handbook of Chemistry and Physics |edition = 84th
 |url = https://archive.org/details/crchandbookofche81lide
 |url-access = registration
 |location = Boca Raton, FL
 |publisher = CRC Press
 |isbn = 978-0-8493-0484-2
}}
</ref>
Like barium and the [[alkali metal]]s, radium crystallizes in the [[body-centered cubic]] structure at [[standard temperature and pressure]]: the radium–radium bond distance is 514.8&nbsp;[[picometer]]s.<ref>{{cite journal
 | last1 = Weigel | first1 = F.
 | last2 = Trinkl | first2 = A.
 | year = 1968
 | title = Zur Kristallchemie des Radiums | language = de
 | trans-title = On radium's chemical chrystalography
 | journal = Radiochim. Acta
 | volume = 10 | issue = 1–2 | page = 78
 | s2cid = 100313675 | doi = 10.1524/ract.1968.10.12.78
}}
</ref>
Radium has a density of 5.5&nbsp;g/cm{{sup|3}}, higher than that of barium, and the two elements have similar [[Crystal structure|crystal structures]] ([[Cubic crystal system|bcc]] at standard temperature and pressure).<ref name="Young">{{cite book |author=Young, David A. |title=Phase Diagrams of the Elements |publisher=University of California Press |year=1991 |isbn=978-0-520-91148-2 |page=85 |chapter=Radium |chapter-url=https://books.google.com/books?id=F2HVYh6wLBcC&pg=PA85}}
</ref><ref>{{cite web
 |title=Crystal structures of the chemical elements at 1&nbsp;bar
 |website=uni-bielefeld.de
 |url=http://wwwhomes.uni-bielefeld.de/achim/ele_structures.html
 |archive-url=https://web.archive.org/web/20140826161012/http://wwwhomes.uni-bielefeld.de/achim/ele_structures.html
 |archive-date=26 August 2014
}}
</ref><!-- books.google.com/books?id=QsgmAAAAMAAJ&q="melting+point+of+radium"&dq="melting+point+of+radium"&hl=de&sa=X&ei=8j_iT72ZAYfOsgb-r91v&ved=0CD4Q6AEwAg books.google.com/books?id=1hNSAAAAMAAJ&q="melting+point+of+radium"&dq="melting+point+of+radium"&hl=de&sa=X&ei=8j_iT72ZAYfOsgb-r91v&ved=0CEgQ6AEwBA -->