Isoelectronic Species
Atoms or ions that possess the same number of electrons and the same electron configuration.
Unit
Dimensionless
In depth
Isoelectronic species share electronic structure but differ in nuclear charge, so their sizes differ systematically: the greater the proton count, the more tightly the same electron cloud is held and the smaller the radius. The concept also predicts similar shapes for isoelectronic molecules and ions.
Examples in the real world
N³⁻, O²⁻, F⁻, Ne, Na⁺ and Mg²⁺ all have 10 electrons, with radii falling from 171 pm to 72 pm; CO and N₂ are isoelectronic.