Narrator: X-ray diffraction with crystals was a new technique when Pauling first put it to use
in 1922 at Caltech. A beam of x-rays is passed through a crystal. The atoms in the
crystal deflect the x-rays onto a photographic plate. From the pattern on the photograph,
it is possible to work out the molecular structure of the crystals. Such as the glycine
molecule. That is, the distance between the atoms, and the angles between the bonds
holding the atoms together. Pauling added another dimension to his work: the mathematically
difficult area of quantum mechanics, then a new branch of physics. Combining quantum
mechanics with x-ray diffraction led him to a powerful new theory on the nature of
the chemical bond.
Linus Pauling: Finally, in December 1930, one day, I thought of a way to get around the mathematical
difficulties – a simplification which made it very easy to get results. And 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. Solve one
equation, and get the answer and solve another equation about the structure of octahedral
complexes such as the ferrocyanide ion in potassium ferrocyanide, or square planar
complexes such as in a tetracholoroplatinate ion and various other problems. I just
kept getting more and more euphorious as time went by and it didn’t take me long to
write a long paper about the nature of the chemical bond, and that was a great experience.
Narrator: That experience helped revolutionize chemistry. It led science to a new understanding
of both the structure and behavior of all matter.
