CHANGE OS ATOMS OVER TIME

Democritus

Lived 400 BC - 370 BC
Atomos Theory

ATOMOS THEORY

• Created the first atomic model
• No electrons, protons, of neutrons
• Experiment - evaporated water exists in air as an independent gas

Aristotle
384 BC - 322 BC
Earth, Wind, Fire, and Water

EARTH WIND FIRE AND WATER

• Did not believe in atomic theory
• Believed all materials are not made of an atom
• Earth wind fire and water created everything

Dalton
1803
Billiard Ball Model

BILLIARD BALL MODEL

• Discovered that certain gases could only be combined in certain proportions
• Suggested first atom
• Said that atoms are invisible

J.J. Thompson
1897
Cathode Ray
Plum Pudding Model

PLUM PUDDING MODEL

• Negative electrons in atom like plum pudding
• Soup of positive charge around center
• Experiment - cathode ray.
• Tried to bend cathode ray with electrical current
• Had to remove gas in tube otherwise it would act as a conductor and not bend the rod

Rutherford
1899
Gold foil
Positively Charged Nucleus Model

POSITIVELY CHARGED NUCLEUS MODEL

• Atoms - tiny, dense, positively charged core called nucleus
• Surrounded by negatively charged electrons
• Like s mini solar system
• Experiment - Gold Foil. Absorbsion of radioactivity
• Observed how many particles would hit the outer circle and create light

Millikan
1909
Oil Drop
Mass/Charge of Electrons

MASS/CHARGE OF ELECTRONS

• Used water droplets to fall into a chamber
• Chamber ionized to remove electrons
• Found that most of electrons are at least 1000 times smaller then an atom
• Experiment - oil drop

Chadwick
1932
Proton Neutron Model

PROTON NEUTRON MODEL

• Found if there were only positive charged proton in nucleus it would break
• Discovered the neutron
• Neutrons can split nucli