Electronic configuration in d-block

According to Bohr-Bury rule, 4f and 5d orbital come after 6s orbital. But if I search for the electronic configuration for Os or any atom in d block for that matter, they give the electronic configuration as 4f 5d 6s instead of 6s 4f 5d


Why does this happen ? why is S orbital written in the end even though it has less energy
Can someone please explain ?




It doesn't matter the way you write it. 4f 5d 6s is the same as 6s 4f 5d. The first one is ordered by energy and the second by the way the orbitals are filled. Even though, you must note that the 5d${^1}$ fills first in the element lanthanum [Xe] 6s2 4f0 5d1 ^[1] <https://en.wikipedia.org/wiki/Electron_configuration>


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Writing 6s orbital at end of electronic configuration indicates that electron will first be removed from 6s orbital then 5d then 4f.
d blocks are exceptional casses. That's why they behave like that.


Example for scandium [Ar] 3d¹4s² indicates that electron will be removed from 4s subshell.


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