Models of the Atom

Humans Try Lots Of Ideas

A Greek philosopher, Democritus, lived about 2500 years ago.

He suggested that matter cannot be divided indefinitely, but must have a smallest entity.

He called this smallest entity the ATOM.

ATOMA = indivisible

Dalton

• Took Democritus’s theory and added scientific data

• An element is composed of the same atoms

• All elements are made out of different atoms

• Each type of atom has a certain mass, size and chemical behavior

J.J. Thompson: Found the Electron

Before the discovery of the nucleus. The main part of the atom had a positive charge and then there were negative charges scattered throughout

The “Marsden” Experiment

Ernest Rutherford

Difference between Plum Pudding and the Rutherford Model

Neils Bohr

Light can excite electrons around atoms and this gives rise to “quantum levels”.

Prince Louis' full name is Louis Victor Pierre Raymond duc de Broglie