ATOMS OVER THE AGES

DEMOCRITUS

ATOMISM

• Divided to a certain point until only atoms remain
• Atoms are indivisible
• Used his atom model to come to these conclusions

ARISTOTLE

FOUR ELEMENTS

• All matter is made up of water, fire, air, earth
• Later influenced alchemy
• According to his theory:
• each element can be transformed into another element,
• if they share a common quality (hot cold dry wet)

DALTON

BILLIARD BALL MODEL

• Determined that atoms were the smallest particle of an atom
• Atoms could not be divided
• In chemical reactions atoms are combined separated or rearranged

J.J. THOMSON

ELECTRONS AND CATHODE RAY

• Plum pudding experiment -electrons
• Led to the cathode ray
• helped to calculate the ratio of
• electric charge to mass of ray

MILLIKAN

OIL DROP

• Measured charge of an electron
• Reaction of oil when dropped between parallel plates
• When voltage added, drop rises
• If rises, indicates upward electrical force > than gravity

RUTHERFORD

GOLD FOIL

• Atom has central positive nucleus
• And surrounded by orbiting electrons
• Most of an atoms mass was in nucleus rest empty space

CHADWICK

NUCLEUS

• No proton-neutron charging
• Neutrons were independent. A 3rd piece of atom
• Not charged like protons or electrons, didn't repel its equal charge