Editing Robert S. Mulliken (section)

===Early scientific career===
From 1926 to 1928, he taught in the [[physics]] department at [[New York University]] (NYU). This was his first recognition as a physicist. Though his work had been considered important by chemists, it clearly was on the borderline between the two sciences and both would claim him from this point on. Then he returned to the University of Chicago as an associate professor of physics, being promoted to full professor in 1931. He ultimately held a position jointly in both the physics and chemistry departments. At both NYU and Chicago, he continued to refine his molecular-orbital theory.

Up to this point, the primary way to calculate the [[electronic structure]] of molecules was based on a calculation by [[Walter Heitler]] and [[Fritz London]] on the [[hydrogen]] molecule (H<sub>2</sub>) in 1927. With the conception of hybridized atomic orbitals by [[John C. Slater]] and [[Linus Pauling]], which rationalized observed molecular geometries, the method was based on the premise that the [[chemical bond|bonds]] in any molecule could be described in a manner similar to the bond in H<sub>2</sub>, namely, as overlapping atomic orbitals centered on the atoms involved.  Since it corresponded to chemists' ideas of localized bonds between pairs of atoms, this method (called the '''Valence-Bond (VB)''' or '''Heitler-London-Slater-Pauling (HLSP)''' method), was very popular. In attempting to calculate the properties of excited states (molecules that have been excited by an energy source), the VB method does not always work well. With its description of the electron wave functions in molecules as delocalized molecular orbitals that possess the same symmetry as the molecule, Hund and Mulliken's molecular-orbital method, including contributions by [[John Lennard-Jones]], proved to be more flexible and applicable to a vast variety of types of molecules and molecular fragments, and has eclipsed the valence-bond method. As a result of this development, he received the Nobel Prize in Chemistry in 1966.

Mulliken became a member of the [[United States National Academy of Sciences|National Academy of Sciences]] in 1936, the youngest member in the organization's history at the time.<ref>{{Cite web |title=Robert S. Mulliken |url=http://www.nasonline.org/member-directory/deceased-members/52287.html |access-date=2023-05-03 |website=www.nasonline.org}}</ref> He was elected to the [[American Philosophical Society]] in 1940 and the [[American Academy of Arts and Sciences]] in 1965.<ref>{{Cite web |title=APS Member History |url=https://search.amphilsoc.org/memhist/search?creator=Robert+S.+Mulliken&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced |access-date=2023-05-03 |website=search.amphilsoc.org}}</ref><ref>{{Cite web |title=Robert Sanderson Mulliken |url=https://www.amacad.org/person/robert-sanderson-mulliken |access-date=2023-05-03 |website=American Academy of Arts & Sciences |date=9 February 2023 |language=en}}</ref> He was elected a [[List of Fellows of the Royal Society elected in 1967|Foreign Member of the Royal Society (ForMemRs) in 1967]].<ref name="frs"/>

[[Mulliken population analysis]] is named after him, a method of assigning charges to atoms in a molecule.