I had begun to think about the theory of the chemical bond very seriously in 1926, '27, after quantum mechanics was discovered and then in 1928 I published a paper, a preliminary paper, and said that I would write more later on. I didn't write anything more for three years because the problem turned out to be such a hard problem, the mathematical problem, that I couldn't solve it.
— Linus Pauling
Modern
Chemical bond theory, peace activism
