Making Light
We need a model of the atom that will explain why atoms emit only certain wavelengths.
First of all, what is the size of a typical atom? Let’s take water (although that is a molecule), since we know a lot about water: its mass density: 1 gm / 1 cc, it is H2O so it has 18 grams/mole, and we know Avagadro’s number = 6.02 x 1023 molecules/mole.