2.6e-36

4.6e-36

5.8e-34

3.6e-34

6.8e-38

Each atom contains a small, dense, positively charged nucleus

Neutral atoms contain an equal number of protons and electrons

Atoms have an even distribution of positive charge and scattered negative charge

Atoms contain a small dense nucleus with an equal number of protons and neutrons

Ernest Rutherford

J.J. Thomson

Niels Bohr

Max Planck

The positively-charged atomic nucleus is concentrated to a tiny fraction of the total atomic volume, most of which is occupied by the electron cloud

Protons, neutrons, and electrons are evenly dispersed in the space occupied by an atom

Protons and neutrons are similar in mass, while electrons have a significantly smaller mass

Protons have a charge of , while electrons have a charge of and neutrons are uncharged

The plum pudding model of atoms was postulated

The neutron was discovered

The mass of an electron was calculated

The charge of an electron was calculated

J.J. Thomson's cathode ray tube experiment proved the existence of a small negatively charged particle, which he named the electron

Robert Millikan's cathode ray tube experiment proved the existence of a small negatively charged particle, which he named the electron

J.J. Thomson was able to deduce the mass of the electron following his experiments using oil drops

From the oil drop experiment, Dalton calculated the mass of the electron to be

Robert Millikan was able to find the charge-to-mass ratio of the electron after conducting experiments using cathode ray tubes

J.J. Thomson was able to find the charge-to-mass ratio of the electron after conducting experiments using cathode ray tubes

Using the charge-to-mass ratio, Robert Millikan was able to deduce the mass of the electron

J.J. Thomson proved the existence of the electron when he showed that the cathode rays were repelled by the negative pole of an electric field