Two or more @[email protected] are described as isoelectronic if they have the same number of @[email protected] electrons and the same structure, i.e. number and @[email protected] of atoms, but differ in some of the elements involved. Thus: CO, N2 and NO+ are isoelectronic. CH2=C=O and CH2=N=N are isoelectronic. and have the same number of electrons, but have different structures, hence they are not described as isoelectronic.