Isoelectronicity Explained
Isoelectronicity is an effect observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electron configurations, but differ by what specific elements are at certain locations in the structure.
For example,,, and are isoelectronic, while and = are not.
This definition is sometimes termed valence isoelectronicity. Definitions can sometimes be not as strict, sometimes requiring identity of the total electron count and with it the entire electron configuration.[1] More usually, definitions are broader, and may extend to allowing different numbers of atoms in the species being compared.[2]
In quantum mechanics, hydrogen-like atoms are ions with only one electron such as . These ions would be described as being isoelectronic with hydrogen.
The atom and the ion are isoelectronic because each has five valence electrons, or more accurately an electronic configuration of [He] 2s2 2p3.
Similarly, the cations,, and and the anions,, and are all isoelectronic with the atom.
,,, and are isoelectronic because each has two atoms triple bonded together, and due to the charge have analogous electronic configurations (is identical in electronic configuration to so is identical electronically to).
(acetone) and (azomethane) are not isoelectronic. They do have the same number of electrons but they do not have the same structure.
http://www.iun.edu/~cpanhd/C101webnotes/chemical-bond/isoelectronic.html Isoelectronic Configurations
A. A. Aradi & T. P. Fehlner, "Isoelectronic Organometallic Molecules", in F. G. A. Stone & Robert West (eds.) Advances in Organometallic Chemistry Vol. 30 (1990), Chapter 5 (at p. 190) google books link
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