Linus Pauling and The Nature of the Chemical Bond: A Documentary History Narrative  
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The Optimist
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In the early 1930s, Pauling was publishing an average of one significant piece of work every five weeks, most of it on the chemical bond or new molecular structures. By the end of this period he had moved almost entirely away from wrestling with the wave equation. "About 1933 or 1934 I gave up on the idea of myself making very complicated quantum-mechanical calculations about molecular structure," he said. "I made a lot of simple quantum-mechanical calculations and drew conclusions, and realized that if you could ever make really accurate quantum-mechanical calculations you wouldn't learn anything from them because they would just agree with the experiment."

He had developed his own "semiempirical" style, combining a broad application of Schrödinger’s wave mechanics with model building and structural data from X-ray crystallography, then matching his results with other laboratory data from across the field of chemistry. It was a very fruitful approach. Through the early 1930s he racked up success after success until, by 1935, he wrote, "I felt that I had an essentially complete understanding of the nature of the chemical bond."

Slowly, his new vision of chemistry began to be accepted by other chemists. Pauling was a persuasive salesman as well as a good researcher. He forwarded his concepts in a flood of articles, appearances and letters. He forwarded his vision to a generation of chemistry students who took his classes at Caltech. He used his skill as a public speaker, his ability to communicate in the language of chemists, his eagerness to travel widely, and his courage (some would say rashness) to publish theoretical insights without a rigorous grounding in hard mathematics.

But one reason stood out above all: his optimism. In 1935, two observers describing the recent advances in quantum chemistry for the Review of Modern Physics could have had Pauling in mind when they wrote, "To be satisfied, one must adopt the mental attitude and procedure of an optimist rather than a pessimist. The latter demands a rigorous postulational theory, and calculations devoid of questionable approximation or of empirical appeals to known facts. The optimist, on the other hand, is satisfied with the approximate solutions of the wave equation. . . He appeals freely to experiment to determine constants, the direct calculation of which would be too difficult. The pessimist, on the other hand, is eternally worried because the omitted terms in the approximation are usually rather large, so that any pretense of rigor should be lacking. The optimist replies that the approximate calculations do, nevertheless, give one an excellent 'steer' and a very good idea of 'how things go,' permitting the systematization and understanding of what could otherwise be a maze of experimental data codified by purely empirical valence rules."

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Audio Clip  Audio: Pauling's Greatest Impact on Chemistry. 1977. (0:59) Transcript and More Information

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See Also: "Hybridization of Bond Functions." May 13, 1934. 
See Also: "The Chemical Bond and the Structure of Molecules" 1935. 

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Linus Pauling, in Painted Canyon, California. 1935.

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"The Strength of Bond Orbitals." 1934.

"By 1935...I felt that I had an essentially complete understanding of the nature of the chemical bond."

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