Elements like N and period 2 elements have endothermic EA. What's the explanation for that as isn't it usually exothermic?

Does this also imply that some elements subsequent EA is exothermic instead of endothermic?(this sounds impossible but I don't know)

  • 1
    $\begingroup$ Answer to the second part here. chemistry.stackexchange.com/questions/170991/… $\endgroup$ Jun 16, 2023 at 13:18
  • $\begingroup$ The total orbital angular momentum contribution is zero for these elements. Leading to the symmetrical effect described in the answer below. $\endgroup$
    – M06-2x
    Jun 16, 2023 at 17:01

1 Answer 1


The 2nd electron affinity is endothermic for all elements.

Only $\ce{Be}$, $\ce{N}$, $\ce{Ne}$ from the 2nd period have negative electron affinity.

Notice that all elements with the negative electron affinity(*) have kind of "pseudo noble gas" configuration, in sense of having about spherical symmetry of electron density distribution in valence orbitals. It means the whole group of valence orbitals is half or fully filled.

See Wikipedia: Electron affinity data_page

(*) Or, at least their electron affinity is shifted toward zero compared to their neighbours.


Not the answer you're looking for? Browse other questions tagged or ask your own question.