Linus Pauling · The chemical bond
How do atoms hold on to each other?
That time, that place
Chemists knew the ratios in which atoms combine — carbon takes four bonds, oxygen two, hydrogen one. Why, they did not know. There were rules and no reasons.
Why this question
With quantum mechanics it became possible to calculate how electrons are distributed in an atom.
What Pauling did was carry that physics into chemistry — treating bonding not as a rule but as a question about electrons.
What was found
One of his findings was that atomic orbitals blend to form orbitals of new shape.
In carbon, four such blended orbitals reach toward the corners of a tetrahedron. That is why carbon's molecules are three-dimensional rather than flat, and why the molecules of life have the shapes they do.
He also showed that bonds lie on a continuum between wholly one-sided and evenly shared, and devised a way to put a number on where a given bond falls.
Then he turned the tools on life itself. Drawing atoms to scale on paper with correct bond angles and folding it, he worked out how a protein chain coils.
There were rules for how atoms bond, and no reasons
Paper models drawn to scale and folded, checked against X-ray diffraction data
He also attacked the structure of DNA and got it wrong, proposing a triple helix. His campaign against nuclear testing brought a second Nobel, making him the only person to win two unshared prizes in different fields. His late advocacy of megadose vitamin C, however, lacked evidence