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History of Atom Discoveries: Democritus to Schrödinger

Explore the key scientists and their discoveries in the history of the atom, from Democritus theorizing the concept of atoms to Schrödinger's understanding of atom neutrality. Learn about atomic theories, the discovery of electrons, nucleus, and energy levels. Understand the mass of protons, neutrons, and electrons and their importance in forming an atom's overall mass.

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History of Atom Discoveries: Democritus to Schrödinger

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  1. Chapter 3 The History of the Atom

  2. I. The Scientists and their Discoveries • Democritus 1. Date = 400 B.C 2. Discovery = Theorized the smallest unit of an element 3. Importance = gave the term and definition of atom

  3. Democritus ATOM Smallest particle

  4. B. John Dalton 1. Date = 1803 2. Discovery = a. Every element is made of atoms b. atoms of same element exactly the same c. Atoms of different elements join together to form molecules

  5. 3. Importance = proposed the ATOMIC THEORY Atomic Theory = 1. everything is made up of atoms 2. atoms make up molecules 3. atoms of the same element are the same

  6. John Dalton Atomic Theory Molecules made of atoms

  7. C. J.J. Thomson 1. Date = 1898 2. Discovery = a. discovered electrons b. electrons are negative 3. Importance = atoms have bothnegative and positive particles

  8. J.J. Thomson “Plum Pudding” model Electrons are negative

  9. D. Ernest Rutherford 1. Date = 1911 2. Discovery = a. discovered nucleus b. did a “gold foil” experiment c. atoms mostly made of space 3. Importance = a. nucleus is very tiny, and positivelycharged b. electronsoutside of nucleus

  10. Ernest Rutherford Discovered nucleus Electrons outside nucleus Gold Foil Experiment

  11. E. Niels Bohr 1. Date = 1913 2. Discovery = a. Electrons are in energy levels b. s, p, d, f orbitals c. 1st = 2 electrons; 2nd = 8 electrons; 3rd = 18 electrons 4th = 32 electrons

  12. 3. Importance = electrons orbit around nucleus in a certain pathway This is the Bohr Model

  13. Niels Bohr Electrons in energy levels

  14. F. Schrödinger 1. Date = present 2. Discovery = electrons are impossible to find ( a moving fan) 3. Importance = a. Atoms are neutral b. atoms must have the samenumber of protons and electrons

  15. Schrödinger Atoms have no charge Same number of protons and electrons

  16. II. The Mass of Atom A. Protons 1. are positively charge 2. have a mass of 1.67 X 10-27 kg 3. Found in the nucleus B. Neutrons 1. Neutral 2. have a mass of 1.67 X 10-27 kg 3. Found in the nucleus

  17. C. Electrons 1. are negatively charged 2. Have a mass of 9.11 X 10-31 kg = 0 atom mass 3. Found orbiting outside the nucleus, so their mass does not effect the atom’s mass!

  18. Section Question • Which scientist gave us the word atom? 2. Which scientist made up the atomic theory? 3. Every element is made of atoms, atoms of the same element are exactly the same, different atoms make up molecules. These statements make up the what?

  19. 4. Which scientist discovered the electrons? 5. Which scientist discovered the nucleus? 6. Which scientist discovered that electrons where in energy levels? 7. Which scientist said atoms where neutral because they had equal number of protons and electrons?

  20. 8. What is the mass of protons? 9. What is the mass of neutrons? 10. What is the mass of electrons? 11. Which part of the atom has the least amount of mass?

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