Isoelectronicity is a phenomenon observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electronic configurations, but differ by what specific elements are at certain locations in the structure. For example, CO, NO+ , and N 2 are isoelectronic, while CH 3COCH 3 and CH 3N=NCH 3 are not.[1]
Carbon monoxide molecule
Nitrosonium ion
Carbon monoxide and nitrosonium are isoelectronic
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 electronic configuration.[2] More usually, definitions are broader, and may extend to allowing different numbers of atoms in the species being compared.[3]
The importance of the concept lies in identifying significantly related species, as pairs or series. Isoelectronic species can be expected to show useful consistency and predictability in their properties, so identifying a compound as isoelectronic with one already characterised offers clues to possible properties and reactions. Differences in properties such as electronegativity of the atoms in isolelectronic species can affect reactivity.
CO, CN− , N 2, and NO+ are isoelectronic because each has two atoms triple bonded together, and due to the charge have analogous electronic configurations (N− is identical in electronic configuration to O so CO is identical electronically to CN− ).
Molecular orbital diagrams best illustrate isoelectronicity in diatomic molecules, showing how atomic orbital mixing in isoelectronic species results in identical orbital combination, and thus also bonding.
More complex molecules can be polyatomic also. For example, the amino acidsserine, cysteine, and selenocysteine are all isoelectronic to each other. They differ by which specific chalcogen is present at one location in the side-chain.
CH 3COCH 3 (acetone) and CH 3N 2CH 3 (azomethane) are not isoelectronic. They do have the same number of electrons but they do not have the same structure.
^Isoelectronic Configurations 2017-07-17 at the Wayback Machineiun.edu
^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
April 12, 2024
isoelectronicity, confused, with, isoelectric, phenomenon, observed, when, more, molecules, have, same, structure, positions, connectivities, among, atoms, same, electronic, configurations, differ, what, specific, elements, certain, locations, structure, examp. Not to be confused with Isoelectric Isoelectronicity is a phenomenon observed when two or more molecules have the same structure positions and connectivities among atoms and the same electronic configurations but differ by what specific elements are at certain locations in the structure For example CO NO and N2 are isoelectronic while CH3 COCH3 and CH3 N NCH3 are not 1 Carbon monoxide moleculeNitrosonium ionCarbon monoxide and nitrosonium are isoelectronic 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 electronic configuration 2 More usually definitions are broader and may extend to allowing different numbers of atoms in the species being compared 3 The importance of the concept lies in identifying significantly related species as pairs or series Isoelectronic species can be expected to show useful consistency and predictability in their properties so identifying a compound as isoelectronic with one already characterised offers clues to possible properties and reactions Differences in properties such as electronegativity of the atoms in isolelectronic species can affect reactivity In quantum mechanics hydrogen like atoms are ions with only one electron such as Li2 These ions would be described as being isoelectronic with hydrogen Examples edit nbsp Serine nbsp Cysteine nbsp SelenocysteineThree isoelectronic amino acids nbsp Dimethyl ether nbsp AzomethaneBoth molecules have the same electron configuration but due to the double bond and extra atom in azomethane they are not isoelectronic The N atom and the O ion are isoelectronic because each has five valence electrons or more accurately an electronic configuration of He 2s2 2p3 Similarly the cations K Ca2 and Sc3 and the anions Cl S2 and P3 are all isoelectronic with the Ar atom CO CN N2 and NO are isoelectronic because each has two atoms triple bonded together and due to the charge have analogous electronic configurations N is identical in electronic configuration to O so CO is identical electronically to CN Molecular orbital diagrams best illustrate isoelectronicity in diatomic molecules showing how atomic orbital mixing in isoelectronic species results in identical orbital combination and thus also bonding More complex molecules can be polyatomic also For example the amino acids serine cysteine and selenocysteine are all isoelectronic to each other They differ by which specific chalcogen is present at one location in the side chain CH3 COCH3 acetone and CH3 N2 CH3 azomethane are not isoelectronic They do have the same number of electrons but they do not have the same structure See also editIsolobal principleReferences edit IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 isoelectronic doi 10 1351 goldbook I03276 Isoelectronic Configurations Archived 2017 07 17 at the Wayback Machine iun edu A A Aradi amp T P Fehlner Isoelectronic Organometallic Molecules in F G A Stone amp Robert West eds Advances in Organometallic Chemistry Vol 30 1990 Chapter 5 at p 190 google books link Retrieved from https en wikipedia org w index php title Isoelectronicity amp oldid 1212985453, wikipedia, wiki, book, books, library,
