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
- 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.