ATOMIC THEORY

DEMOCRITUS

ATOMOS

• All mater is made of small, invisible particle
• These small, invisible particles were called atoms
• Didn't perform any specific experiments
• His theory was kept alive by Lucretius
• Named the atom after Greek word Atomos

ARISTOTLE

EARTH WIND FIRE WATER ELEMENTS

• All substances are compounds of four elements
• Four elements are earth, wind, fire, and water
• Suggested around 450 BC by ancient Greeks
• This theory is now known to be incorrect

DALTON

BILLIARD BALL MODEL

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

THOMSON

PLUM PUDDING MODEL

• Idea formed from the cathode ray experiment
• Law of conversation of mass
• Discovered existence of electrons
• Electrons were the negatively charged particles
• The area surrounding it was positively charged

RUTHEFORD

POSITIVELY CHARGED NUCLEUS MOLECULE

• Brought up in reaction to the Gold Foil experiment
• Positive charge in an atom focused in the nucleus
• Nucleus surrounded by negatively charged ions
• Mass of an atom concentrated mainly in the nucleus

MILLIKAN

MASS/CHARGE OF ELECTRONS

• Oil Drop experiment
• Determines size and charge of electrons
• Very similar to Thomson's experiment
• Extremely small mass

CHADWICK

PROTON NEUTRON MODEL

• Student of Rutherford's
• Discovered the neutron
• Atom consists of protons, neutrons, and electron
• Neutrons have no charge
• Protons and neutrons are in the nucleus