The Prize:
The 1954 Nobel Prize in Chemistry was awarded to Linus Pauling “for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances.”
The Science:
Linus Pauling has been honoured by many as the greatest modern chemist. A Nobel Prize was definitely in his destiny, but Pauling himself wasn’t sure what he would win it for.
His contribution to chemistry is a story of a career’s worth, with no single great achievement—something that Alfred Nobel had stipulated as necessary for Nobel Prize–winning work.
Pauling’s interest in the chemical bond started during undergrad. At this time, the model for the chemical bond, the “glue” that keeps two atoms in a molecule bound to each other, was thought of as “hooks and eyes” like the clasps found at the top of some zippers. Every atom had a certain number of hooks and eyes to attach to other atoms, and joining a hook and an eye from different atoms resulted in the formation of a chemical bond.
Pauling’s own work on chemical bonds was highly influenced by the work of Gilbert Lewis and Irving Langmuir (Nobel Laureate, 1932). The Lewis and Langmuir model of the atom posited that the electrons that orbit the nucleus of an atom can be found in orbital shells: the first shell contains two electrons, with the remaining electrons found in subsequent, larger shells that hold eight electrons each. In their model, the atom is “happiest” when the outermost shell is full. Thus, an atom that has seven electrons in its outermost shell will bond to an atom with only one electron in its outer shell, allowing them to “share” that electron, and making both atoms “happier.”
Of course, this model was too simplistic to explain what chemists at the time knew about atoms. The scientific community was already beginning to think of electrons as waves and not as moons orbiting a nuclear planet.
After completing his PhD in 1925, Pauling spent time in Europe on a Guggenheim Fellowship working with quantum theory giants Arnold Sommerfield, Niels Bohr (Nobel Laureate, 1922), and Erwin Schrödinger (Nobel Laureate, 1933). Exposure to the world of theoretical physics allowed Pauling to start his own lab at Caltech in a very new field, quantum chemistry, where he could explore the connection between quantum mechanics and the chemical bond.
Pauling’s Nobel-winning work began in 1928, when he published a theory on the nature of the carbon bond. His paper hypothesized that the formation of chemical bonds resulted in the exchange of energy, an idea originally proposed by Walter Heitler and Fritz London. This theory addressed a long-standing debate between physicists and chemists over carbon’s bonding geometry. The paper did not include any mathematics to back up Pauling’s hypothesis, but he set out to prove it mathematically and finally did, three years later.
In 1931, Pauling wrote the first in a series of seven papers describing “The Nature of the Chemical Bond.” Using quantum mechanics and wave functions, Pauling derived the strengths and arrangements of bonds and predicted other properties of bonds not yet discovered. “I was so excited and happy, I think I stayed up all night, making, writing out, solving the equations, which were so simple that I could solve them in a few minutes,” he said at the time.
Pauling was one of the few chemists familiar with quantum theory, making his theories easily 10 years ahead of everyone else’s. Einstein famously said, “It was too complicated for me,” to a reporter after sitting in on a seminar given by Pauling in 1931.
Each successive article in the “Nature of the Chemical Bond” series built upon the theories of part one, and described a different aspect of the chemical bond. The third paper in the series outlined the differences between covalent bonds (when two atoms share an electron virtually equally) and ionic bonds (when one atom takes the lion’s share of the electron time). He demonstrated that bonds in intermediate states between covalent and ionic could be explained by quantum mechanics and chemical observations.
Pauling’s fourth paper in the series described the famous electronegativity scale. Unlike the other papers which were heavy on theoretical physics, this paper was intuitive and the science was easy for other chemists to understand. Pauling’s electronegativity scale is a measure of how hard an atom can “tug” on an electron shared in a chemical bond. When an atom with a high “tugging” power shares an electron with a lower pull, the bond they share is more likely to be ionic. The scale allowed chemists to predict what type of bond two atoms will form when they react.
In the early 1930s, Pauling was publishing an average of one manuscript every five weeks—an impressive rate even today. Throughout this prolific period, he also devoted much time to teaching. He was known as an excellent lecturer and could make even the most difficult concepts easy to understand.
His teaching influenced another of his major works, The Nature of the Chemical Bond and the Structure of Molecules and Crystals: An Introduction to Modern Structural Chemistry, a textbook aimed at graduate-level chemistry students that revolutionized the way chemistry was taught. It focused on how the quantum mechanics of a chemical bond can influence molecular structure and therefore the behaviour and properties of molecules. Max Perutz (Nobel Laureate, 1962) said that Pauling’s textbook showed that “chemistry could be understood rather than being memorized.” It quickly became accepted as a standard text and was translated into many languages.
The next stage of Pauling’s career moved away from chemistry and into biology. He made significant contributions to protein chemistry, genetics, and immunology. With others he determined the molecular mechanism behind sickle cell anemia. Pauling also contributed to the discovery of secondary structure elements in proteins that allow proteins to fold into functional forms. James Watson and Francis Crick rushed their work to explain the structure of DNA because they perceived that Pauling might discover it before them—they beat him and won the Nobel Prize in 1962. He also made valuable contributions to the war effort during the Second World War.
Yet, the Nobel Prize eluded him. It was only in 1954—over 20 years after his original contributions—that Pauling was finally honoured by the Nobel committee. Pauling first heard about his award from a reporter, first asking “what did I get it for?” He was happy to hear that he had won the award for his work since 1928. The committee had bent the rules and awarded Pauling an award for years of achievement.
Pauling’s influence on almost every branch of science is undeniable. He revolutionized the way scientists thought about chemistry. Francis Crick called Pauling “the father of molecular biology” and Pauling’s name can be heard in the same breath of such great thinkers as Newton, Galileo, and Einstein.
What you may not know:
After years of waiting for his Nobel in Chemistry, Pauling was soon afterwards awarded the Nobel Peace Prize in 1962. The second award made Pauling the only scientist to be singly awarded a Nobel Prize in two different categories.
This Nobel Prize was awarded to Pauling for his work from 1946 onwards in campaigning against the building, testing, and use of nuclear arms in war. In 1946, Pauling, Einstein, and seven other scientists founded the Emergency Committee of Atomic Scientists to prevent the use of nuclear weapons from ever again creating the disasters seen in both Hiroshima and Nagasaki, Japan.
With aid and inspiration from his wife, Ava Helen Pauling, he wrote an appeal against nuclear weapons that was signed by 2,000 American scientists and 8,000 scientists abroad to petition the American government and the United Nations. Pauling wrote the book No More War! describing the collection of these signatures. He and Ava worked tirelessly on organizing conferences to promote peace.
For his work against nuclear weapons, Pauling was stripped of his passport by the American government and prevented from attending a scientific lecture tour of Europe because he was seen as a communist sympathizer and was described by the Senate Internal Security Subcommittee as “the number one scientific name in virtually every major activity of the Communist peace offensive” in America. He was reissued his passport in order to attend his Chemistry Nobel Prize ceremony in 1954.
The Chair of the committee concluded his presentation speech to Pauling with the words: “Should Linus Pauling, through his tireless efforts, have contributed—if only a little—to restoring to science its ideals, then his campaign will in itself have been of such value that we living today can scarcely appreciate the full extent of the debt we owe him.”
