ATOMS

DEMOCRITUS

ATOMOS MODEL

• All matter is composed of tiny,individual particles
• Atomos- indivisible
• Thus, atoms cannot be divided or cut

ARISTOTLE

EARTH WIND FIRE WATER ELEMENTS

• Everything is made up of these 4 elements...not by atoms
• Was against what Democratus was saying
• Mislead people for many years because of this false theory

DALTON

BILLIARD BALL MODEL

• Atoms make up all matter
• Cannot be subdivided, created, or destroyed but can be rearranged (supports the Law of Conservation of Matter)
• Atoms can combine and form compounds in chemical reactions
• Compounds of different elements form in whole number ratios
• Weights of an atom can be distinctive

JJ THOMSON

PLUM PUDDING MODEL

• Suggested an atom's # of electrons are relative to its atomic #
• Balanced by positive charge
• PPM Model is a sphere of + and - charged filling containing electrons
• Like cookie dough batter or plum pudding!
• CATHODE RAY- tried 3 experiments to determine structure of atom by using a "not so uncommon" cathode ray tube

MILLIKAN

MASS/CHARGE OF ELECTRON

• OIL DROP EXPERIMENT- charged droplets of oil suspended between 2 metal electrodes
• Could determine the charge on oil drops in mechanical equilibrium
• Charge of a single electron: 1.5924(17)*10-19(superscript)

RUTHERFORD

POSITIVELY CHARGED NUCLEUS MODEL

• GOLD FOIL- aimed beam of alpha particles at gold foil...observing where beam of particles landed
• If PPM Model was correct, particles would go through the gold...but sometimes they bounced back
• Thus, changing the definition and drawing of an atom not as protons, neutrons,and electrons inside...
• But as a positively charged nucleus with protons and electrons surrounding it.

CHADWICK

PROTON NEUTRON MODEL

• # of protons = # of neutrons
• Protons AND neutrons in nucleus
• Electrons surround (possibly orbit) the nucleus