or no valency at all. No atomic model, so far as I know, has succeeded in making this difference plausible; but it is not essential to the hypothesis, that, independently of any atomic model:—(i ...

In 1913, Niels Bohr revised Rutherford's model by suggesting that the electrons ... However, there was still a difference between the atomic number of the atom and the atomic mass.

He concluded that all matter was made of tiny particles called atoms. He suggested that an atom was a tiny solid ball. He published his ideas in 1803. This atomic model has changed over time.