ATOMIC TIMELINE

DEMOCRITUS

• 460 BC
• Theory: Atomos Model

ATOMOS THEORY

• All matter is made up of very small particles
• Atoms can neither be created or destroyed in a chemical reaction
• Atoms of different elements have different masses and chemical properties

AROSTOTLE

EARTH, WIND, FIRE, WATER

• Earth: cold and dry
• Wind: hot and moist
• Fire: hot and dry
• Water: cold and moist

DALTON

BILLIARD BALL MODEL

• Solid invisible sphere with no moving parts
• Model for composition of matter
• Matter is build from small, indestructible particles

THOMSON

EXPERIMENT: CATHODE RAY

• Plum Pudding Model
• - Discovered the electron
• - Proposed Plum Pudding Model with positive and negative charge filling sphere only one ten billionth of a metre across
• - Found that Cathode rays were super concentrated charge

RUTHERFORD

EXPERIMENT: GOLD FOIL

• Positive charged nucleus model
• - The atom is 99.99% empty space
• - The nucleus contains a positive charged
• - The nucleus is approx. 100,000 time smaller than the atom

MILLIKAN

EXPERIMENT: OIL DROP

• Mass/Charge of Electron
• - Electron could be removed from atoms
• - Cathode rays used to create beams of light
• - Balanced electric and magnetic fields

CHADWICK

PROTON NEUTRON MODEL

• Number of protons in the nucleus are equivalent to the positive charge of the atom
• Idea that there could be a particle with mass but no change
• Nucleus was made of a positively charged neutron