JOHN DALTON

JOHN

• All matter made up of invisible particles called atoms
• Atoms of the same element are identical; atoms of different elements are different
• Atoms of different elements combine in the whole number ratios to form compounds.
• Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

J.J. THOMPSON

Made a piece of equipment called a cathode ray tube. It is a vacuum tube- all the air has been pumped out.
He discovered the electron.

ERNEST RUTHERFOLD

RUTHERFOLD

• Beleived in Thompson's plum pudding model of the atom
• Wanted to see what whole big particles were
• 1910-Gold foil expirement
• Used radioactivity (alpha particles)

NEILS BOHR

Concluded experiments to update Rutherford's model.
Said that the electrons move around the nucleus in fixed orbits that have a set amount(levels) of energy.

JAMES CHADWICK

Discovered the neutron: same mass as the proton, but no charge.

Einstein
Heisenberg
Pauli

Heisenberg's uncertainty principle: the position and the momentum of a particle(electron) cannot be simultaneously measured with arbitrarily high precision.