I have this difficult question that has stumped almost any physicist or chemist i've asked.. so i'm asking you guys, spectroscopy specialists.. Is there a difference between NIST data and HF calculations, on 3d and 4s in neutral scandium? For example In this article by Geoffrey Neuss https://www.thinkib.net/chemistry/page/37492/the-electron-configuration-of-scandium In his Figure 3 https://www.thinkib.net/media/ib/chemistry/images/2023-topics/s2-models-of-bonding---structure/fig-2-ca.png He has 3d and 4s in afbau order for neutral scandium. So 4s lower than 3d. From what I understand, this goes against the established idea in chemistry that for neutral scandium, 3d and 4s swap from afbau order. So as mentioned, from what I understand, it's well established in chemistry that in neutral scandium, 3d and 4s switch from the afbau position , for neutral scandium. So 3d lower than 4s. And we see that here. in this paper from Vanquickenborne, following the established view. https://pubs.acs.org/doi/abs/10.1021/ed071p469 Transition Metals and the Aufbau Principle L. G. Vanquickenborne, K. Pierloot, and D. Devoghel Figure 1 shows a graph, https://www.chemedx.org/sites/www.chemedx.org/files/fig05_vanquickenborne.jpg Not asking about before Potassium re that graph. From it shows that among neutral atoms, once neutral scandium is reached, so Z=21, then 4s and 3d switch round.. And from enquiries i've made as to the numbers. " The graph in Figure 1 is only qualitative (no scale is given). The numbers at the basis of this graph result from a numerical Hartee-Fock calculation (exact within the one-electron approximation) for the 4s²3d1 ground state configuration of Scandium (with 3 valence electrons). More details on the calculational method and the numerical results can be found in reference 3 of the paper on the Aufbau principle: it refers to a 1989-paper by the same authors in Inorganic Chemistry. The numerical values of the orbitals are given there in Table III: €(3d) = - 9.353 eV and €(4s) = - 5.717 eV, situating 4s about 3.8 eV higher than 3d." So then the question is, what are Neuss's numbers coming from.. I did see somebody mention, that they think it comes from here . This page on NIST for energy levels on neutral scandium https://physics.nist.gov/cgi-bin/ASD/energy1.pl?de=0&spectrum=Sc+I&submit=Retrieve+Data&units=0&format=0&output=0&pagesize=15&multipletordered=0&confout=on&termout=on&levelout=on&uncout=1&jout=on&landeout=on&perc_out=on&biblio=on&temp= (You could use this shorter URL if you prefer, it goes to the same page on physics.nist.gov http://tinyurl.com/yhp36hns ) I don't think Neuss goes into where he got the 138kJ/mol number from But It looks like maybe he picked the ~11500 cm^-1 number from the first few rows of the NIST data. I see from this unit converter https://www.weizmann.ac.il/oc/martin/tools/hartree.html 11500cm^-1 = 137.5kJ/mol So that's his 138kJ/mol I'm no expert and there's clearly a difference there in the two sources re positions of 3d and 4s in neutral scandium. What do you guys think about it.. e.g. do the NIST data and HF data contradict.. Or is the NIST data being misinterpreted there? Does a correct interpretation of the NIST data actually support vanquickenborne and not Neuss? Would you say Vanquickenborne's view is the mainstream and not Neuss? Thanks asked Jan 04 at 10:34 |