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Development of the atomic theory

Development of the atomic theory. Important laws. Law of conservation of mass Mass is neither created or destroyed during ordinary chemical reactions or physical changes. All the matter that has ever existed still exists and always will

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Development of the atomic theory

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  1. Development of the atomic theory

  2. Important laws • Law of conservation of mass • Mass is neither created or destroyed during ordinary chemical reactions or physical changes. • All the matter that has ever existed still exists and always will • It can change form or location but can always be accounted for.

  3. Important laws • Law of definite proportions • A chemical compound always contains the same elements in the same proportions by mass. • Law of multiple proportions • If two or more different compounds are formed from the same elements then the masses of the second element when the first remains constant is always a small whole number.

  4. Dalton’s Atomic Theory • All matter is composed of extremely small particles called atoms • Atoms of a given element are identical in size, mass and other properties. Atoms of different elements differ in size, mass and other properties. • Atoms cannot be subdivided, created or destroyed

  5. Dalton’s Atomic Theory continued • Atoms of different elements combine in simple whole-number ratios to form chemical compounds • In chemical reactions, atoms are combined, separated or rearranged.

  6. First modification to Dalton’s Theory Mid to late 1800’s Major advancement in society was…. Use of electricity Scientists had a new toy

  7. JJ Thomson 1897

  8. Thomson’s findings: • A green beam travelled from the • Cathode to the anode. • There was nothing in the tube except • the metal plates that made the • electrodes • The beam had a mass and a negative • charge.

  9. Conclusions: • The beam is made of particles • From the cathode • The particles,called electrons, • have a negative charge • 0.0065g of electrons have 6.02x1023 • negative charges • The negative charges come from the • atoms in the metal plate • Atoms can be broken into smaller • particles.

  10. Now that we know the atom has parts……….. Discovery of them begins. atoms are neutral atoms have neative charged particles therefore there must also be…. positive parts that balance out the negative.

  11. What might that look like? First attempt: JJ Thomson

  12. The model failed………… There was no experiment that confirmed it. There was an experiment that contradicted it.

  13. Along came Rutherford… • New Zealander • Hired to head a team to study the • atom. • Extremely well known for his • discoveries

  14. Gold foil experiment is His most famous. Although it was carried out by Geiger and Marsden

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