Bohr Model of Hydrogen

The atomic theory of matter has a long history, in some ways all the way back to the ancient Greeks (Democritus ca. 400 BCE suggested that all things are composed of indivisible “atoms”). From what we can observe, atoms have certain properties and behaviors, which can be summarized as follows: Atoms are small, with diameters on the order of 0.1 nm. Atoms are stable, they do not spontaneously break apart into smaller pieces or collapse. Atoms contain negatively charged electrons, but are electrically neutral. Atoms emit and absorb electromagnetic radiation. Any successful model of atoms must be capable of describing these observed properties.