I am aware of the definition of electron affinity and electron gain enthalpy (EGE). N has positive EGE1, and EA of P,S,Cl is more than N,O,F respectively. I want to arrange them in order of their EA2 in periods and groups.

My attempt : F,Cl attain noble gas and it's EA would be close to IE (ionization energy) of alkali metals, so, quite small. O and S would be halogen with quite high EA. P and N would be S and O so, somewhere in between the above two.

Hence, O>N>F and S>P>Cl.

for groups, I would still say that 3rd period would have more EA than 2nd but the only data that I have (from another chemistry.stack question) is 2nd EA of O is more than S.

Some help regarding data availability of EA2 is needed and fault in my logic.

  • $\begingroup$ I think several of those dianions are actually unbound (i.e. no activation energy towards ionization back to the monoanion), which makes measuring the second electron affinities very hard, if not entirely ill-defined. $\endgroup$ Commented Jan 14, 2017 at 6:26
  • $\begingroup$ It seems bonkers that I could not find any data. Surely EA 2 would help out in stability of ions and ionization energy of anions. I just hope somebody has something on this. $\endgroup$
    – Mrigank
    Commented Jan 14, 2017 at 7:27


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