The History of the Atom

Democritus

400 BCE

Democritus did not actually experiment to get his findings. He theorized the idea of the atom. His theory was that an atom was an indivisible piece of matter that was mainly composed of empty space.

John Dalton

1800

Dalton was a considered to be a "coarse investigator". However, his main theories are atoms are solid ball like structures that are indivisible, they are able to be combined with other atoms to create new chemicals, and they cannot be created or destroyed. He also found atomic weights however did not explain how he found his atomic weights.

J. J. Thomson

1890

Thomson is credited with the discovery of the electron. He found them when experimenting with gas discharge tubes. He noticed movement and decided to call it cathode rays. These cathode rays moved from the negative side to the positive side because the rays were made of negatively charged particles, electrons.

Lord Ernest Rutherford

1920

Rutherford is famous for finding that atoms were mainly made up of empty space. He found this when doing something called a gold fs is whe1920re he shot alpha particles at gold foil and found that most went straight through. What was most revolutionary though were the particles that were slightly deflected. This is because it found that the nucleus is positively charged.

Niels Bohr

1930

Niels Bohr is credited for the current model of the atom. It is similar to a solar system. Bohr found where electrons belong in an atom and how they have levels that keep each electron their based on their charge.