Isoelectronic Definition - Chemistry Glossary

Isoelectronic refers to two atoms, ions, or molecules that have the same electronic structure and the same number of valence electrons. The term means equal electric or equal charge. Isoelectronic chemical species typically display similar chemical properties. Atoms or ions with the same electronic configurations are said to be isoelectronic to each other or to have the same isoelectronicity. Related Terms: Isoelectronicity, Valence-Isoelectronic Isoelectronic Examples The K ion is isoelectronic with the Ca2 ion. The carbon monoxide molecule (CO) is isoelectronic to nitrogen gas (N2) and NO. CH2CO is isoelectronic to CH2NN. CH3COCH3 and CH3NNCH3 are not isoelectronic. They have the same number of electrons, but different electron structures. The amino acids cysteine, serine, tellurocysteine, and selenocysteine are isoelectronic, at least with respect to valence electrons. More Examples of Isoelectronic Ions and Elements Isoelectronic Ions/Elements Electron Configuration He, Li+ 1s2 He, Be2+ 1s2 Ne, F- 1s2 2s2 2p6 Na+, Mg2+ 1s2 2s2 2p6 K, Ca2+ [Ne]4s1 Ar, S2- 1s2 2s2 2p6 3s2 3p6 S2-, P3- 1s2 2s2 2p6 3s2 3p6 Uses of Isoelectronicity Isoelectronicity may be used to predict the properties and reactions of a species. It is used to identify hydrogen-like atoms, which have one valence electron and are thus isoelectronic to hydrogen. The concept may be applied to predict or identify unknown or rare compounds based on their electronic resemblance to known species.