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Atomic Theory: the beginning

Atomic Theory: the beginning. Chapter 3 Part I. Democritus. An Ancient Greek Theorized about the existence of atoms. Did not use Scientific Method. John Dalton. A school teacher in England. Worked out his ideas at home. Used Scientific Method. Dalton’s Atomic Theory.

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Atomic Theory: the beginning

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  1. Atomic Theory: the beginning Chapter 3 Part I

  2. Democritus • An Ancient Greek • Theorized about the existence of atoms. • Did not use Scientific Method.

  3. John Dalton • A school teacher in England. • Worked out his ideas at home. • Used Scientific Method.

  4. Dalton’s Atomic Theory • All Elements are composed of tiny indivisible particles called atoms. • Atoms of the same element are identical. Atoms of one element are different from any other element. • Atoms of different elements can physically mix or chemically combine with one another in simple whole number ratios. • Chemical reactions occur when atoms are separated, joined, or rearranged as a result of a chemical reaction.

  5. Dalton’s Atomic Theory

  6. Electrons • Atoms are know to be divisible. • One part of the atom, the electrons are negatively charged subatomic particles. • These were discovered by JJ Thomson.

  7. Possible video of Cathode Tubes • http://www.chem.uiuc.edu/clcwebsite/cathode.html

  8. FoxTrot

  9. Millikan and the charge of an electron • http://www.britannica.com/nobel/cap/omillik001a4.html • Robert Millikan carried out experiments that allowed him to calculate the charge and mass of an electron. Charge is one unit and mass is 1/1840 the mass of a hydrogen atom.

  10. Protons • E. Goldstein observed a cathode-ray tube and discovered rays traveling in the opposite direction. • He called these canal rays and That they had a positive charge. • We now call them protons. Their mass is 1840 times and electron

  11. Neutrons • James Chadwick confirms the existence of the neutron. These have no charge but add weight to the atom.

  12. How did the modern atomic model develop? • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf

  13. Development of Atomic model • It all started with Plum Pudding. • Not this Plum Pudding!!

  14. This is JJ Thompson’s Plum Pudding Model

  15. Rutherford’s Model • Rutherford realized from his experiments that the positively charged particles had converged into a small “nucleus” in the center of the atom and were surrounded by the very small electrons.

  16. Bohr’s model • Bohr took Rutherford’s model one step further and theorized the electrons orbit the nucleus.

  17. Common View: But is it correct?

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