Describing compounds that have the same numbers of valence electrons. For example, nitrogen (N2) and carbon monoxide (CO) are isoelectronic molecules.
Chemistry
Denoting different molecules that have the same number of electrons. For example N2 and CO are isoelectronic. The energy level diagrams of isoelectronic molecules are therefore similar.
Electronics and Electrical Engineering
Denoting groups of atoms that have identical distributions of electrons in the outer orbits, and exhibit similar electronic properties.