Editing Barium (section)

===Physical properties===
[[File:Barium 1.jpg|thumb|left|Oxidized barium]]
Barium is a soft, silvery-white metal, with a slight golden shade when ultrapure.<ref name="Ullman2005">{{Ullmann |last1=Kresse|first1=Robert|last2=Baudis|first2=Ulrich|last3=Jäger|first3=Paul|last4=Riechers|first4=H. Hermann|last5=Wagner|first5=Heinz|last6=Winkler|first6=Jochen|last7=Wolf|first7=Hans Uwe|title=Barium and Barium Compounds|date=2007 |doi=10.1002/14356007.a03_325.pub2|isbn=9783527306732}}</ref>{{rp|2}} The silvery-white color of barium metal rapidly vanishes upon [[redox|oxidation]] in air yielding a dark gray layer containing the [[Barium oxide|oxide]]. Barium has a medium [[specific weight]] and high electrical conductivity. Because barium is difficult to purify, many of its properties have not been accurately determined.<ref name="Ullman2005" />{{rp|2}}

At room temperature and pressure, barium metal adopts a [[body-centered cubic]] structure, with a barium–barium distance of 503 [[picometer]]s, expanding with heating at a rate of approximately 1.8{{e|-5}}/°C.<ref name="Ullman2005" />{{rp|2}} It is a soft metal with a [[Mohs hardness]] of 1.25.<ref name="Ullman2005" />{{rp|2}} Its melting temperature of {{convert|1000|K|C F}}<ref name="Lide2004">{{cite book|last = Lide |first= D. R. |title = CRC Handbook of Chemistry and Physics |url = https://archive.org/details/crchandbookofche81lide |url-access = registration |edition = 84th |location = Boca Raton (FL) |publisher = CRC Press |date = 2004 |isbn = 978-0-8493-0484-2}}</ref>{{rp|4–43}} is intermediate between those of the lighter strontium ({{convert|1050|K|C F|disp=or}})<ref name="Lide2004" />{{rp|4–86}} and heavier radium ({{convert|973|K|C F|disp=or}});<ref name="Lide2004" />{{rp|4–78}} however, its boiling point of {{convert|2170|K|C F}} exceeds that of strontium ({{convert|1655|K|C F|disp=or}}).<ref name="Lide2004" />{{rp|4–86}} The density (3.62&nbsp;g/cm<sup>3</sup>)<ref name="Lide2004" />{{rp|4–43}} is again intermediate between those of strontium (2.36&nbsp;g/cm<sup>3</sup>)<ref name="Lide2004" />{{rp|4–86}} and radium (≈5&nbsp;g/cm<sup>3</sup>).<ref name="Lide2004" />{{rp|4–78}}