All elements whose EA have been measured using modern methods have a positive electron affinity, but older texts mistakenly report that some elements such as alkaline earth metals have negative Eea, meaning they would repel electrons. This is not recognized by modern chemists. The electron affinities of the noble gases have not been conclusively measured, so they may or may not have slightly negative EAs. Atoms whose anions are relatively more stable than neutral atoms have a greater Eea. Chlorine most strongly attracts extra electrons; mercury most weakly attracts an extra electron. Eea of noble gases are close to 0.
|Alkali metals||Alkaline earth metals||Lanthanides||Actinides||Transition metals|
|Poor metals||Metalloids||Nonmetals||Halogens||Noble gases|
A trend of decreasing Eea going down the groups in the periodic table would be expected. The additional electron will be entering an orbital farther away from the nucleus, and thus would experience a lesser effective nuclear charge. However, a clear counterexample to this trend can be found in group 2A, and this trend only applies to group 1A atoms.
ELECTRON AFFINITIES OF BN, NO AND NF: COUPLED CLUSTER AND MULTIREFERENCE CONFIGURATION INTERACTION CALCULATIONS
Jul 01, 2005; The accurate adiabatic electron affinities (EA) of the BN, NO and NF molecules have been determined using the coupled cluster...