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History of Atomic Structure

History of Atomic Structure. How long have people been interested in understanding matter and its structure? Thousands of years Hundreds of years A few years Never. Ancient Philosophy. Who: Aristotle, Democritus When: More than 2000 years ago Where: Greece

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History of Atomic Structure

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  1. History of Atomic Structure

  2. How long have people been interested in understanding matter and its structure? • Thousands of years • Hundreds of years • A few years • Never

  3. Ancient Philosophy • Who:Aristotle, Democritus • When: More than 2000 years ago • Where: Greece • What: Aristotle believed in 4 elements: Earth, Air, Fire, and Water. Democritus believed that matter was made of small particles he named “atoms”. • Why: Aristotle and Democritus used observation and reasoning to explain the existence of everything.

  4. Democritus Aristotle

  5. Alchemists • Who: Early “Scientists” • When: 500 – 900 years ago • Where: Europe, Asia and Middle East • What: Their work developed into what is now modern chemistry. • Why: Trying to change ordinary materials into gold.

  6. Alchemic Symbols

  7. Particle Theory • Who:John Dalton • When: 1808 • Where: England • What: Described atoms as tiny particles that could not be divided. Thought each element was made of its own kind of atom. • Why: Building on the ideas of Democritus in ancient Greece.

  8. John Dalton

  9. Discovery of electrons • Who:J. J. Thompson • When: 1897 • Where: England • What: Thompson discovered that electrons were smaller particles of an atom and were negatively charged. ‘Plum pudding’ model. • Why:Thompson knew atoms were neutrally charged, but couldn’t find the positive particle.

  10. J. J. Thompson

  11. ‘Solar system’ model • Who: Ernest Rutherford • When: 1911 • Where: England • What: Conducted an experiment to isolate the positive particles in an atom. Decided that the atoms were mostly empty space, but had a dense central core. • Why: He knew that atoms had positive and negative particles, but could not decide how they were arranged.

  12. Ernest Rutherford – born in NZ

  13. Orbits model • Who: Niels Bohr • When: 1913 • Where: England • What: Proposed that electrons traveled in fixed paths around the nucleus. Scientists still use the Bohr model to show the number of electrons in each orbit around the nucleus. • Why: Bohr was trying to show why the negative electrons were not sucked into the nucleus of the atom.

  14. Bohr’s Model Niels Bohr

  15. Electron cloud model • Electrons travel around the nucleus in random orbits. • Scientists cannot predict where they will be at any given moment. • Electrons travel so fast, they appear to form a “cloud” around the nucleus.

  16. Electron cloud model

  17. What is the latest? • Scientists have discovered many new smaller parts of an atom. • Find out more!!!!!

  18. Atomic Structure Timeline Requirements: • Must include a title. • Must include a spot for each of the 7 items. • Must include at least the Who, When, and What. • Must have a picture for each item – see atomic model pdf atomic model resource Options: • Flow Map format • Standard timeline

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