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Democritus ’ Atomic Theory

Democritus ’ Atomic Theory. He believed that atoms were indivisible and indestructible. His theory had some flaws. What were they? HE DID NOT USE THE SCIENTIFIC METHOD!!. Aristotle. Impact on western civilization Believed all matter was continuous

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Democritus ’ Atomic Theory

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  1. Democritus’ Atomic Theory • He believed that atoms were indivisible and indestructible. • His theory had some flaws. What were they? • HE DID NOT USE THE SCIENTIFIC METHOD!!

  2. Aristotle • Impact on western civilization • Believed all matter was continuous • Democritus nor Aristotle had zero scientific evidence

  3. Democritus’ Theory Altered…2000 yrs Later • John Dalton began the modern discovery of atoms. • Studied the ratio in which elements combine in a chemical reaction. • He formulated hypotheses and theories on the results of his experiments.

  4. Dalton’s Atomic Theory • All elements are composed of tiny indivisible particles called atoms. • Atoms of the same element are identical. • Atoms of different elements can physically mix or chemically combine in whole-number ratios. • Chemical reactions occur when atoms are separated, joined or rearranged.

  5. Dalton’s Theory ALTERED! • Atoms are made up of even smaller particles! (They are Divisible) • 3 subatomic particles: • Protons • Neutrons • Electrons

  6. Electrons! (Corpuscules) • Discovered by J.J. Thomson • Plum Pudding Model • Electrons – Negatively charged subatomic particles (-1)

  7. Protons! • Discovered by Eugen Goldstein and J.J. Thomson • Observed a cathode-ray tube, and found rays traveling in the opposite direction. • What does this mean?

  8. Last but not least, NEUTRONS! • Discovered by James Chadwick • Subatomic particles with NO charge

  9. The Atomic Nucleus • Rutherford’s Gold Foil Experiment • Used alpha particles to penetrate thin gold foil. • SOME DEFLECTED BACK! • Nucleus: Tiny central core of the atom

  10. Things Rutherford’s Atomic Model Could Explain • Protons and Neutrons composed the atomic nucleus • Electrons move around the nucleus in the same way that planets revolve around the sun

  11. How can all these Theories change? • SCIENTIFIC METHOD • Make observations • Hypothesize – testable prediction • Experimentation • Revise Hypothesis • Formulate Theory - explanation based on observations and supported by results from experimentation

  12. Rutherford’s Model Changed! • 1913 – The Bohr Model • Energy of an atom changes when it absorbs or emits light • Electrons are only found in specific circular paths, or orbits around the nucleus • Each possible orbit have fixed energy levels

  13. Another Atomic Model is Developed • 1926Schrodinger (Used Mathematical Solutions) • Quantum Mechanical Model – determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus

  14. Where can you find electrons? • Atomic Orbitals – region in space in which there is a high probability of finding an electron • Principle energy levels (n = 1) • Energy sublevels (1)

  15. What is nuclear force?

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