Robert S. Mulliken

Lore & Background

As a child, he learned plant classification and helped with editorial work on his father's four-volume text on organic compound identification, becoming an expert in organic chemical nomenclature. Mulliken earned his B.S. Conant. After the war, he earned his Ph.D.

Reader's Guide

Robert Mulliken's primary contribution was the development of molecular orbital theory, which describes electrons in molecules as delocalized orbitals extending over the entire molecule, in contrast to the valence-bond method that treated bonds as localized between atom pairs. This approach, also called the Hund-Mulliken theory, proved more flexible for calculating excited states and a wide variety of molecular types, eventually eclipsing the valence-bond method. Mulliken also derived a scale for measuring electronegativity based on the average of an atom's ionization enthalpy and electron affinity, and developed Mulliken population analysis for assigning charges to atoms in molecules.

Did You Know?

• Mulliken learned German well enough to skip scientific German in college but could not remember his high school German teacher's name.
• He conducted his first publishable research as an undergraduate at MIT on the synthesis of organic chlorides.
• Mulliken was hospitalized for months during World War I after suffering burns from his laboratory work and later contracting influenza.