Democritus contributed to our understanding of the atom in which of the following ways?
1. he determined the mass of the electron.
2. he determined the charge-to-mass ratio for the electron.
3. he hypothesized that all substances can be broken down into a smallest part called the atom.
4. he discovered the proton.

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .

it is the most commonly accepted one