Linus Pauling - Career

Career

Pauling was first exposed to the concepts of quantum mechanics while studying at Oregon State University. He later traveled to Europe on a Guggenheim Fellowship, which was awarded to him in 1926, to study under German physicist Arnold Sommerfeld in Munich, Danish physicist Niels Bohr in Copenhagen and Austrian physicist Erwin Schrödinger in Zürich. All three were experts in the new field of quantum mechanics and other branches of physics. Pauling became interested in how quantum mechanics might be applied in his chosen field of interest, the electronic structure of atoms and molecules. In Zürich, Pauling was also exposed to one of the first quantum mechanical analyses of bonding in the hydrogen molecule, done by Walter Heitler and Fritz London. Pauling devoted the two years of his European trip to this work and decided to make it the focus of his future research. He became one of the first scientists in the field of quantum chemistry and a pioneer in the application of quantum theory to the structure of molecules. He also joined Alpha Chi Sigma, the professional chemistry fraternity.

In 1927, Pauling took a new position as an assistant professor at Caltech in theoretical chemistry. He launched his faculty career with a very productive five years, continuing with his X-ray crystal studies and also performing quantum mechanical calculations on atoms and molecules. He published approximately fifty papers in those five years, and created five rules now known as Pauling's rules. By 1929, he was promoted to associate professor, and by 1930, to full professor. In 1931, the American Chemical Society awarded Pauling the Langmuir Prize for the most significant work in pure science by a person 30 years of age or younger. The following year, Pauling published what he regarded as his most important paper, in which he first laid out the concept of hybridization of atomic orbitals and analyzed the tetravalency of the carbon atom.

At Caltech, Pauling struck up a close friendship with theoretical physicist Robert Oppenheimer, who was spending part of his research and teaching schedule away from U.C. Berkeley at Caltech every year. The two men planned to mount a joint attack on the nature of the chemical bond: apparently Oppenheimer would supply the mathematics and Pauling would interpret the results. Their relationship soured when Pauling began to suspect that Oppenheimer was becoming too close to his wife, Ava Helen. Once, when Pauling was at work, Oppenheimer had come to their place and blurted out an invitation to Ava Helen to join him on a tryst in Mexico. She flatly refused, and reported the incident to Pauling. Disquieted by this strange chemistry, and her apparent nonchalance about the incident, he immediately cut off his relationship with Oppenheimer.

In the summer of 1930, Pauling made another European trip, during which he learned about the use of electrons in diffraction studies similar to the ones he had performed with X-rays. After returning, he built an electron diffraction instrument at Caltech with a student of his, L. O. Brockway, and used it to study the molecular structure of a large number of chemical substances.

Pauling introduced the concept of electronegativity in 1932. Using the various properties of molecules, such as the energy required to break bonds and the dipole moments of molecules, he established a scale and an associated numerical value for most of the elements – the Pauling Electronegativity Scale – which is useful in predicting the nature of bonds between atoms in molecules.