HISTORY OF THE ATOM

DALTON. WHAT DID HE DO?

- he said that atoms are invisible

- he said that they were solid spheres

JJ THOMPSON. WHAT DID HE DO? WHAT WAS IT CALLED?

- he discovered the electron

- the discovery of a subatomic particle showed that atoms aren't invisible.

-called it the plum pudding model

- it was a model in which there was negatively charged electrons in positively charged space

RUTHERFORD. WHAT DID HE DO?

- he did a lil experiment where he fired positively charged alpha particles at gold foil

- most of them passed straight through, this showed that the atom was MOSTLY empty space.

- HOWEVER, some of the particles were deflected back, this showed that the mass of an atom was concentrated at the centre of the atom AND that the "nucleus" was positively charged.

NEILS BOHR. WHAT DID HE DO?

- he said that if electrons were "free" within the atom, they would be attracted to the nucleus and the atom would collapse on itself.

- so he created a model in which has a small, positively charged central nucleus and electrons orbiting in at specific fixed distances from the nucleus.

CHADWICK. WHAT DID HE DO?

- found neutrons