If an f orbital has 6 unpaired electrons then how many electrons can be exchanged. According to me if 2 electrons are added then a half filled f orbital would be formed which is stable (not as much as a completely filled orbital but still quite stable) however, the answer is supposedly 15.

If one knows the reason please do tell.


1 Answer 1


There are six unpaired electrons, and we can swap any two of them, so we have: $${6\choose2} = 15$$

  • $\begingroup$ However doesn't exchange imply in out transfer?? $\endgroup$ Commented Apr 9, 2017 at 17:59
  • $\begingroup$ Also I'm not able to view your answer properly. I'm seeing a yellow box below your text 'so we have: ' and the yellow box has in it written in red font Undefined control sequence \binom.' I'm not sure what this popup signifies as I'm viewing it for the first time, if you know, please do tell. $\endgroup$ Commented Apr 9, 2017 at 18:36
  • $\begingroup$ I am not familiar with your definition of exchange. The issue you're experiencing may be a MathJax issue, but I am not sure about the specifics. In different notation, my answer is $_6C_2 = 15$. $\endgroup$ Commented Apr 9, 2017 at 19:48
  • $\begingroup$ @a-cyclohexane-molecule for some reason, \binom doesn't currently render in the Android app of SE. I put in a suggestion to edit it to \choose, which uses different syntax, but works in the app. $\endgroup$
    – Tyberius
    Commented Apr 10, 2017 at 1:44
  • $\begingroup$ Ok I get it now. What I was talking about would've been valid if it bad been specified that transfer of electrons is happening. Thanks. $\endgroup$ Commented Apr 10, 2017 at 3:31

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