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THE ONE MAJOR CONTRIBUTION OF EACH OF THE SCIENTISTS UNDERSTANDING THE ATOM DEMOCRITUS • FACTS: • MAJOR CONTRIBUTION: • Believed that: • All matter is made of small, solid objects that can’t be divided, created or destroyed • these small objects should be called “atoms” • Different types of matter are made from different types of atoms • Nothing between these atoms except empty space • Gave us the concept of an “atom” ARISTOTLE • FACTS: • Believed that: • All matter made of fire, water, air, and earth • No empty space existed • Was popular and influential • MAJOR CONTRIBUTION: • Prevented Democritus’s ideas from being studied for more than 2,000 years DALTON • FACTS: • Studied Democritus’s ideas about the atom • Revised the idea of the atom but included many of the same ideas of Democritus: • MAJOR CONTRIBUTION: • Gave us the atomic model THOMSON • FACTS: • MAJOR CONTRIBUTION: • Did experiment with cathode ray tube • Discovered the electron • Discovered that there were particles even smaller than atoms • Discovered that the cathode rays had a small, negatively charged particles • Concluded that atoms contain negative and positively charged particles that balance each other out • “chocolate cookie” model RUTHERFORD • FACTS: • Student of Thomson • Along with his students, did the gold foil experiment • THOUGHT that positively charged alpha particles would pass though the gold foil BUT FOUND that most passed through, SOME bounced off to the side and A FEW bounced straight back • MAJOR CONTRIBUTION: • Discovered that atoms have a nucleus CHADWICK • FACTS: • Colleague of Rutherford • Studied atoms • MAJOR CONTRIBUTION: • Discovered neutrons BOHR • FACTS: • Student of Rutherford • Experiments led to a revised atomic model • MAJOR CONTRIBUTION: • Electrons have specific levels of energy Assignment for Tomorrow: (vocab quiz on 1/6) • In your notebook or on notecards, write definitions for the following words: • Atom • Electron • Nucleus • Proton • Neutron • Electron cloud