Like, do I need to just remember that it is less in 3d than 3s and so on?

  • $\begingroup$ Welcome to ChemSE. Please add some further details to your question which, at present, is very broad (Cf. en.wikipedia.org/wiki/…). $\endgroup$ – Buttonwood Jun 12 '19 at 20:37
  • $\begingroup$ I'm voting to close this question as off-topic because your question lacks context. This question needs revision before it is ready for a great answer. Please edit to include how this question came up and how you tried to answer it. This will help writing an answer that is useful for you and for others. $\endgroup$ – Karsten Theis Jun 12 '19 at 20:42