ATOMIC THEORY PROGRESSION

DEMOCRITUS

ATOMOS

• The word atomos means "cannot be cut"
• Thought atoms were made of the same thing but different shapes and sizes
• Believed matter could not be divided into smaller pieces forever

ARISTOTLE

EARTH, WIND, FIRE, WATER ELEMEMTS

• Greeks claimed these were the original four elements
• Also suggested a fifth element of aether
• Thought all matter was composed of these elements

DALTON

BILLIARD BALL MODEL

• His billiard ball model showed that atoms couldn't be divided
• Believed atoms could not be destroyed by chemical reactions, just rearranged
• Believed atoms were indestructible
• Believed when two or more atoms combine chemically they form compounds.

J.J. THOMPSON

PLUM PUDDING MODEL

• Developed this model using the cathode ray
• Discovered elections and called them corpuscles
• Plus represented a negative charge and the pudding represented a positive charge

RTUHERFORD

POSITIVELY CHARGED NUCLEUS MODEL

• Fired alpha rays through gold foil and the rays went in all different directions
• Wanted to see if the positive charge and the mass of atom were evenly distributed
• Worked with Hans Geiger on the gold foil experiment
• Thought that atoms are mostly empty space ei the positive charged dense at the center which is the nucleus

MILLIKIN

MASS/CHARGE OF ELECTRON

• Used the oil drop experiment to determine the sizeof electron charge
• He put a charge on an oil drop and measured how much of an electric field was needed to stop the drop from falling
• He performed the oil drop experiment with Harvey Fletcher

CHADWICK

POSITIVELY CHARGED NUCLEUS MODEL

• Discovered the neutron
• His findings helped contribute to the fission of uranium 235
• Showed that neutrons can spilt the nuclei of heavy elements