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J.D. Lee Concise Inorganic Chemistry, Appendix E: Electronic Structures of the Elements [1, p. 601] provides two electronic configurations for berkelium:

$$ \ce{Bk}\quad \begin{cases} [\ce{Rn}]~\mathrm{(5f)^9(6d)^0(7s)^2} \\ [\ce{Rn}]~\mathrm{(5f)^8(6d)^1(7s)^2} \end{cases} $$

Why does Wikipedia — Berkelium lists only the following one?

$$\ce{Bk}\quad [\ce{Rn}]~\mathrm{(5f)^9(7s)^2}$$

Which electronic configuration is more appropriate and why does my textbook include both?

Reference

  1. Sudarsan Guha. J.D. Lee Concise Inorganic Chemistry, for JEE (Main & Advanced), 4th ed.; Wiley India Pvt. Ltd.: India, 2017 (reprint 2020). ISBN 978-81-265-9114-5.
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    $\begingroup$ Electronic configurations of such heavy metals do not mean anything. Textbook writers can write whatever conjectures they want. What is the experimental evidence? Who investigated it? Without such info, this electron configuration exercises are just academic exercises. $\endgroup$
    – AChem
    Oct 3, 2022 at 18:36
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    $\begingroup$ Total quantities of Bk produced are in the gram range. Since the discovery of it. The largest batch I can find evidence for was 22mg to be used in heavier element production. $\endgroup$
    – Jon Custer
    Oct 3, 2022 at 19:23
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    $\begingroup$ nature.com/articles/s41467-021-21189-1 has some interesting info on Cf and Bk electronic structure. $\endgroup$
    – Jon Custer
    Oct 3, 2022 at 19:28
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    $\begingroup$ Why would there be only two? $\endgroup$
    – Oscar Lanzi
    Oct 3, 2022 at 19:31

1 Answer 1

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Both of these configurations are appropriate and valid. $\ce{[Rn] {5f^96d^07s^2}}$ or simply $\ce{[Rn] {5f^97s^2}}$ is the ground state electronic configuration of berkelium while $\ce{[Rn] {5f^86d^17s^2}}$ is the electronic configuration of first excited state of berkelium. There is an energy difference of $\ce{0.92 eV}$ between these two states. The enthalpy of vaporization of trivalent Bk metal was calculated to be $\ce{2.99 eV (288 kJ mol^{–1})}$.

The Reference also states

A hybridized nondegenerate 6d and 5f virtual‐bound‐states model has been used to describe the properties of the actinide metals, including berkelium. It accounted for the occurrence of localized magnetism in Bk metal. Included was the relativistic energy band structure of fcc Bk metal, $\ce{[Rn] {5f^86d^17s^2}}$ and the conclusion was that berkelium is a rare earth‐like metal with localized (ionic) 5f electrons resulting from less hybridization with the 6d and 7s itinerant bands than occurs in the lighter actinides.

Reference : The Chemistry of the Actinide and Transactinide Elements, 3rd edition, by Lester R. Morss, Norman M. Edenstein, Jean Fuger & Joseph J. Katz.

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  • $\begingroup$ 0.92 eV is a lot of energy (aprox. 0.03 Hartree) . I do not have access to your source, sure you meant a smaller amount. Please correct. $\endgroup$
    – PAEP
    Jun 18 at 11:16
  • $\begingroup$ I rechecked my source and found that it really is written 0.92 eV. $\endgroup$
    – Proscionexium
    Jun 18 at 11:26
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    $\begingroup$ Thanks. If I am not mistaken, in that case, one of the configurations would correspond to an excited configuration. $\endgroup$
    – PAEP
    Jun 18 at 17:59
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    $\begingroup$ Yes that's exactly what the book says. $\endgroup$
    – Proscionexium
    Jun 18 at 18:06

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