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101
Thales - 620 BC
First person to wonder what made up the world around us. -
101
Democritus - 440 BC
First person to think of an atom. -
101
Aristotle - 340 BC
He thought everything was made up of fire, air, water, and earth. -
Sir Isaac Newton
He contributed to atomic theory. -
John Dalton
He developed an atomic theory.
1. All matter is made up of tiny particles called atoms.
2. All atoms of a given element are alike, but are different from the atoms of any other element.
3. Compounds are formed when atoms of different elements combine in fixed proportions.
4. A chemical reaction involves a rearrangement of atoms, not a change in the atoms themselves. -
Henri Bacquerel
He discovered radioactivity. -
J.J. Thomson
He discovered the electron and developed the plum pudding model. -
Robert Andrews Milliken
He performed the oil drop experiment and found the charge of individual electrons. -
Ernest Rutherford
He performed the gold foil experiment and discovered the nucleus. -
Niels Bohr
He discovered that electrons have orbits. -
Francis Aston
He invented the mass spectrograph and discovered isotopes. -
Erwin Shrodinger
He used math equations to find the probability that an electron would be in a certain location. -
James Chadwick
He discovered the neutron.
