1898, Thomson
Thomson discovered the existence of the subatomic particles called electrons.
This meant that the atomic model had to be changed to include them, so Thomson created the plum-pudding model.
This model depicted tiny, negatively charged electrons floating in a sea of positive charge.
1911, Rutherford
Rutherford concluded that the positive charge in an atom must be concentrated in a small area, which he names the nucleus.
The resulting model from this was called the 'nuclear model'.
He also concluded that atoms must be mostly empty space.
1913, Bohr
Bohr concluded that electrons, to avoid spiralling inwards, must orbit the nucleus at specific distances.
This lead to the proposition of shells.
He created the 'atomic model'
1932, Chadwick
Chadwick discovered particles with no charge and named them neutrons.
He said that they're also found in the nucleus.
He created the 'modern atomic model' which depicts the electrons moving about the nucleus in a cloud.
It is impossible to tell where an electron is at any given time, and it is impossible to predict where it will be.