Democritus (460 BC-370 BC)
Suggests the existence of atoms and that they were indivisible and had an ultimate particle

JOHN DALTON (1766-1844)

• English Chemist who created the atomic theory:
• Each element is composed of tiny indestructible particles called atoms.
• All atoms are identical
• Atoms are combined in a simple, whole number ratios to form compounds.

J.J. THOMSON (1856-1940)

• English physicist who discovered the electron in 1897.
• Did experiments that involved passing an electric current through gases.
• Discovered electrons in a cathode-ray tube.

ERNEST RUTHERFORD (1871–1937)

• In 1911, he decided to test the plum pudding model of atomic structure
• Passed particles through gold
• 98% went through, 2% were deflected

NIELS BOHR

• Created a model showing that electrons travel in orbits around the nucleus
• The farther the electron is from the nucleus, the more energy it has

ERWIN SCHRÖDINGER

• Discovered an equation that predicts the probability in finding an electron