- 1904: J.J Thomson proposes the first scientific model of the atom, which he dubs the Plum Pudding Model stemming from his discovery of the electron. In this model, atoms themselves are positively charged by nature and contain enough negatively charged electrons inside them to be neutralised. However, there is no notion of shells or orbits.
- 1909: Ernest Rutherford’s gold foil experiment, contradicts the plum pudding model, as he fires alpha particles towards an atom, and instead of very small deflections (due to the small and weakly charged electrons), he noticed most particles went through the atom, and the ones that didn’t were very strongly deflected.
- 1911: Rutherford proposes the Rutherford Model based on his results from the gold foil experiment.
- 1885 - 1908: Observation of discrete lines in hydrogen atomic spectra dis