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Democritus 400 BC

Democritus 400 BC. Ancient Greek philosopher who thought that matter was made of small indivisible particles. He name them “atoms” which means indivisible in Greek. John Dalton 1830. Agreed with Democritus model of the atom and Added to Democritus idea.

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Democritus 400 BC

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  1. Democritus400 BC

  2. Ancient Greek philosopher who thought that matter was made of small indivisible particles. He name them “atoms” which means indivisible in Greek

  3. John Dalton1830

  4. Agreed with Democritus model of the atom and Added to Democritus idea

  5. Agreed with Democritus that matter was made of small indivisible particles. His model was the atom was tiny solid spheres. Each element had a different size sphere

  6. He created an atomic theory that consisted of 4 parts1) Chemical elements are made up of atoms. 2) The atoms of an element are identical in their masses. (Be sure students understand that this was shown to be false with the discovery of isotopes.) 3) Atoms of different elements have different masses. 4) Atoms only combine in small, whole number ratios such as 1:1, 1:2,

  7. J.J. Thomson1897

  8. Found that atoms are divisible by discovering the electrons

  9. Used a cathode ray tube to discover electrons (negative particles)Thought the negative particles were mixed in the positive charge like raisins in plum pudding

  10. Ernest Rutherford1908

  11. Was a former student of J.J Thomsondisproved his idea of the plum pudding model

  12. Thought that the atom is mostly empty space.(football stadium model)discovered the nucleus by doing an experiment with gold foil

  13. Niels Bohr1913

  14. Worked under J.J. Thomson and Ernest Rutherford to improve the model of the atom

  15. Thought that electrons orbit the nucleus like planets orbit the sun. We still draw atoms like this today.

  16. Electron Cloud Theory1920’s

  17. States that electrons don’t stay in fixed orbits. They can move from one energy level to another. This model is more like a ceiling fan. You know were the blades are but you can pinpoint one blade

  18. First energy level can have 2 electronssecond can have 8third can have up to 18 (but it prefers 8) and the 4th can have up to 32

  19. Protons

  20. Positive chargefound in the nucleusweighs 1 amu (atomic mass unit)

  21. Electron

  22. Negative chargefound in the electron cloud surrounding the nucleustakes almost 2000 of them to weigh as much as one proton or neutron

  23. Neutron

  24. No charge (neutral)found in the nucleusweight one amu

  25. Atomic number

  26. Number of protonsunique to each element

  27. Atomic mass

  28. Number of protons and neutrons combined

  29. Isotope

  30. Atoms of the same element with a different number of neutrons

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