Why is the radius of Europium so unusually high and out of the general trend ? Moreover, at different sources I am getting different values of radii. In some (e.g., Wikipedia) the radii are following the regular trend and in some Europium has been shown to be bigger. (Source : NCERT Class 12 Chemistry Part-1)

NCERT Class 12 Chemistry Part-1

  • $\begingroup$ What do the other sources say? $\endgroup$ – Eashaan Godbole Mar 6 '19 at 14:30

Well spotted! I dare say, the book appears to have used a covalent radius for Europium, while using atomic radii for the other lanthanides.

See "atomic radius" vs "covalent radius" values: for Europium, Samarium, and Gadolinium.

Also see this article if you don't like my referencing Wikipedia :P

  • $\begingroup$ For what it's worth, a similar trend is given in Housecroft and Sharpe's Inorganic Chemistry, 4th ed. In there, both Eu and Yb have anomalously large "atomic radii" (199 and 194 pm respectively), which could be related to this: chemistry.stackexchange.com/questions/53960/… I assume that these radii relate to the interatomic separation in the metal. $\endgroup$ – orthocresol Mar 6 '19 at 21:34

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