ATOMS

DEMOCRITUS

ATOMOS MODEL

• Originally a round sphere with no electrons, protons, and neutrons
• It was the first atomic model
• It helped scientists look into further makeup of the atom

ARISTOTLE

EARTH, WIND, FIRE, WATER ELEMENTS

• All substances were made up of the four elements
• Earth was the center of the universe

JOHN DALTON

BILLIARD BALL MODEL

• All matter is composed of atoms
• Atoms can not be created or destroyed
• Atoms in a given element are identical in mass and properties
• Different elements have different types of atoms

J. J. THOMSON

PLUM PUDDING MODEL

• Electrons are surrounded by postive charges
• Positive charges balance out the negative charges
• The model helped people understand the atom's general makeup
• Thomson also developed the Cathode Rays experiment

ERNEST RUTHERFORD

POSITIVELY CHARGED NUCLEUS MODEL

• The atom is 99.99% empty space
• The nuleus contains a positive charge and most of the mass of the atom
• Nucleus is 100,000 times smaller tan the aton
• He discovered this information through the Gold Foil experiment

ROBERT ANDREWS MILLIKAN

MASS/CHARGE OF ELECTRON

• Discovered actual charge and mass values
• With the discovery of one came the calculation of the other
• Used the oil-drop experiment to measure the charge of the electron

JAMES CHADWICK

PROTON NEUTRON MODEL

• Repeated experiments of past scientists in search of a neutral particle
• Was able to determine that the neutron existed
• Its mass is about 0.1% bigger than a proton's