Editing Lanthanide (section)

====Hydrides====
{| class="wikitable collapsible collapsed" style="font-size:95%;"
|-
![[Chemical element]]!![[Lanthanum|La]]!![[Cerium|Ce]]!![[praseodymium|Pr]]!![[neodymium|Nd]]!![[promethium|Pm]]!![[samarium|Sm]]!![[europium|Eu]]!![[gadolinium|Gd]]!![[terbium|Tb]]!![[dysprosium|Dy]]!![[holmium|Ho]]!![[erbium|Er]]!![[thulium|Tm]]!![[ytterbium|Yb]]!![[lutetium|Lu]]
|-
| [[Atomic number]]
|57||58||59||60||61||62||63||64||65||66||67||68||69||70||71
|-
|Metal lattice (RT)
|dhcp ||fcc ||dhcp ||dhcp ||dhcp ||r ||bcc ||hcp ||hcp ||hcp ||hcp||hcp ||hcp ||hcp ||hcp
|-
|Dihydride<ref name="Fukai">{{cite book |last=Fukai |first=Y. |year=2005 |title=The Metal-Hydrogen System, Basic Bulk Properties, 2d edition|publisher=Springer|isbn=978-3-540-00494-3}}</ref>
|LaH<sub>2+x</sub>||CeH<sub>2+x</sub>||PrH<sub>2+x</sub>  ||[[Neodymium(II) hydride|NdH<sub>2+x</sub>]]|| ||SmH<sub>2+x</sub>  ||[[europium hydride|EuH<sub>2</sub>]] o <br> "salt like"||GdH<sub>2+x</sub> ||TbH<sub>2+x</sub> ||DyH<sub>2+x</sub> ||HoH<sub>2+x</sub>  ||ErH<sub>2+x</sub> ||TmH<sub>2+x</sub>   ||[[Ytterbium hydride|YbH<sub>2+x</sub>]] o, ''fcc''<br> "salt like" ||LuH<sub>2+x</sub>
|-
| style="padding-left: 2em" |''Structure''
|[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||*[[lead(II) chloride|PbCl<sub>2</sub>]]<ref name="KohlmannYvon2000">{{cite journal|last1=Kohlmann|first1=H.|last2=Yvon|first2=K.|title=The crystal structures of EuH<sub>2</sub> and EuLiH<sub>3</sub> by neutron powder diffraction|journal=Journal of Alloys and Compounds|volume=299|issue=1–2|year=2000|pages=L16–L20|doi=10.1016/S0925-8388(99)00818-X}}</ref>  ||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||[[calcium fluoride|CaF<sub>2</sub>]]||  ||[[calcium fluoride|CaF<sub>2</sub>]]
|-
| style="padding-left: 2em" |''metal sub lattice''
|''fcc''||''fcc''||''fcc''||''fcc''||''fcc''||''fcc''||''o''||''fcc''||''fcc''||''fcc''||''fcc''||''fcc''||''fcc''||''o'' ''fcc''||''fcc''
|-
|Trihydride<ref name="Fukai"/>
|LaH<sub>3−x</sub>||CeH<sub>3−x</sub> ||PrH<sub>3−x</sub>||[[Neodymium(III) hydride|NdH<sub>3−x</sub>]] ||||SmH<sub>3−x</sub>  ||EuH<sub>3−x</sub><ref name="MatsuokaFujihisa2011">{{cite journal|last1=Matsuoka|first1=T.|last2=Fujihisa|first2=H.|last3=Hirao|first3=N.|last4=Ohishi|first4=Y.|last5=Mitsui|first5=T.|last6=Masuda|first6=R.|last7=Seto|first7=M.|last8=Yoda|first8=Y.|last9=Shimizu|first9=K.|last10=Machida|first10=A.|last11=Aoki|first11=K.|title=Structural and Valence Changes of Europium Hydride Induced by Application of High-Pressure H<sub>2</sub>|journal=Physical Review Letters|volume=107|issue=2|pages=025501|year=2011|doi=10.1103/PhysRevLett.107.025501|pmid=21797616|bibcode=2011PhRvL.107b5501M}}</ref> ||GdH<sub>3−x</sub>||TbH<sub>3−x</sub> ||DyH<sub>3−x</sub> ||HoH<sub>3−x</sub>||ErH<sub>3−x</sub>  ||TmH<sub>3−x</sub> ||||LuH<sub>3−x</sub>
|-
|style="padding-left: 2em" |''metal sub lattice''
|''fcc''||''fcc''||''fcc''||''hcp''||''hcp''||''hcp''||''fcc''||''hcp''||''hcp''||''hcp''||''hcp''||''hcp''||''hcp''||''hcp''||''hcp''
|-
|Trihydride properties<br> transparent insulators <br>(color where recorded)
|red ||bronze to grey<ref name="TellefsenKaldis1985">{{cite journal|last1=Tellefsen|first1=M.|last2=Kaldis|first2=E.|last3=Jilek|first3=E.|title=The phase diagram of the Ce-H<sub>2</sub> system and the CeH<sub>2</sub>-CeH<sub>3</sub> solid solutions|journal=Journal of the Less Common Metals|volume=110|issue=1–2|year=1985|pages=107–117|doi=10.1016/0022-5088(85)90311-X}}</ref> ||PrH<sub>3−x</sub> ''fcc''||NdH<sub>3−x</sub> ''hcp'' ||||golden greenish<ref name="KumarPhilip2002">{{cite journal|last1=Kumar|first1=Pushpendra|last2=Philip|first2=Rosen|last3=Mor|first3=G. K.|last4=Malhotra|first4=L. K.|title=Influence of Palladium Overlayer on Switching Behaviour of Samarium Hydride Thin Films|journal=Japanese Journal of Applied Physics|volume=41|issue=Part 1, No. 10|year=2002|pages=6023–6027|doi=10.1143/JJAP.41.6023|bibcode=2002JaJAP..41.6023K|s2cid=96881388 }}</ref> ||EuH<sub>3−x</sub> ''fcc'' ||GdH<sub>3−x</sub> ''hcp'' ||TbH<sub>3−x</sub> ''hcp''||DyH<sub>3−x</sub> ''hcp'' ||HoH<sub>3−x</sub> ''hcp''||ErH<sub>3−x</sub> ''hcp'' ||TmH<sub>3−x</sub> ''hcp'' ||||LuH<sub>3−x</sub> ''hcp''
|}

Lanthanide metals react exothermically with hydrogen to form LnH<sub>2</sub>, dihydrides.<ref name="Fukai"/> With the exception of Eu and Yb, which resemble the Ba and Ca hydrides (non-conducting, transparent salt-like compounds), they form black, [[pyrophoricity|pyrophoric]], conducting compounds<ref name="Holleman"/> where the metal sub-lattice is face centred cubic and the H atoms occupy tetrahedral sites.<ref name="Fukai"/> Further hydrogenation produces a trihydride which is [[non-stoichiometric compound|non-stoichiometric]], non-conducting, more salt like. The formation of trihydride is associated with and increase in 8–10% volume and this is linked to greater localization of charge on the hydrogen atoms which become more anionic (H<sup>−</sup> hydride anion) in character.<ref name="Fukai"/>