I know this is a correct image, but I am a bit confused because I have seen different versions. If the 3rd orbital can take 18 electrons, why does it suddenly have 8 valence electrons on the 4th orbital, and then another electron on the 5th. I have seen other examples where the 4th orbital goes up to 32 electrons. How do I know when to use which ? I believe it might have to do with the complexity of the atom. Could someone please explain it in simpler terms

Couldn't attach the picture so I have the link here: https://commons.wikimedia.org/wiki/File:37_rubidium_(Rb)_enhanced_Bohr_model.png

  • $\begingroup$ The diagonal principle can be used to memorize electronic configuration. $\endgroup$ – DHMO Jan 16 '17 at 23:49
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    $\begingroup$ The name for the diagonal filling process is typically given as the Aufbau principle. en.wikipedia.org/wiki/… $\endgroup$ – MaxW Jan 16 '17 at 23:50
  • $\begingroup$ I think images have to be jpg not png. $\endgroup$ – MaxW Jan 16 '17 at 23:51
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    $\begingroup$ see chemistry.stackexchange.com/questions/18466/… $\endgroup$ – Mithoron Jan 16 '17 at 23:57

The electron configuration of an Rubidium atom can be written like this: enter image description here You are correct, the 4th Shell may hold a maximum of 32 electrons. However, electrons are arranged in a way so they have the least energy. As you can see above, the 4th shell is not completely filled because orbital 5s is a lower energy orbital, thus preferred over 4d. This principle applies to all atoms.

A easy method to remember is via the Aufbau principle:

enter image description here

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