I was in chemistry class at Rose-Hulman circa 1982, and the professor explained an abstract situation with a P/N junction, using only the equilibrium equations

I was in chemistry class at Rose-Hulman circa 1982, and the professor explained an abstract situation with a P/N junction, using only the equilibrium equations from chemistry. I was immersed in the details, when he backed out of the abstraction, and said... that's how diodes work! Then he did junction transistors. I'll never forget that feeling of awe, but I've forgotten the details.