history of the atom

Democritus 430 BC

Matter is formed of small pieces that could not be cut into smaller parts called atomos (uncuttable)

Dalton 1808

Atoms are invisible particles

2. atoms of one element are all the same

3. atoms of different element are different

4. compounds form by combing atoms

Thomson 1847

Atoms are made mostly out of (+) charged material, like dough in a bun. The (-) charged electrons are found inside (+) dough (pudding)

Rutherford  1911

Atoms have (+) particies in the center, and are mostly empty space. (+) particles

called protons, the center of atoms called nucleus (gold foil experiment)

Bohr 1913

improved on Rutherford's model.

He proposed that electrons move around

the nucleus in specific layers, or shells.

Every atom has a specific number of electrons shell

Chadwick 1932

Worked with Rutherford to discover particles with no charge called neutrons. Neutrons are also found in the nucleus

Democritus

model 

Thomson

model

Rutherford

model

Bohr

model