ATOMIC THEORY TIMELINE

DEMOCRITUS

• All matter consists of invisible particals call atoms
• Atoms are indestructible
• Atoms are solid but invisible
• Atoms are homogenous
• Atoms differ in size, shape, mass, position, arrangement

ARISTOTLE

• Believed all materials in earth were made from fire, wind, earth and water
• Every substance was made of small amounts of each of these four elementsof matter
• He developed the atomic theory

DALTON

• Elements consisted of tiny particals called atoms
• An element is pure because all atoms of an element are identical
• All of the atoms that make up an element have the same mass
• A compound is a pure due to different elements bonded together

JJ THOMSON

• Discovered electrons and noticed that an atom can be divided
• Atoms are made of positive cores and negatively charged particals within it
• Developed the Plum Pudding Model
• Electrons are surrounded by a "pudding" of positive charges to balance the negative

RUTHERFORD

• First to split an atom
• Awarded for Nobel prize
• Did the gold foil experement, which showed that every atom has a nucleus

MILLIKAN

• Measured the charge on an electron
• Oil-drop apparatus
• Challenged Einstein multiple times

CHADWICK

• Credited for discovering the neutron
• He was knigted
• He was awarded for a nobel prize