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1.3 – ATOMIC THEORY

1.3 – ATOMIC THEORY. OBJECTIVES. By the end of the lesson you should be able to: Describe how the atomic theory was developed and who was involved in the process Draw and describe an atom using 4 major properties. HISTORICAL UNDERSTANDING.

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1.3 – ATOMIC THEORY

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  1. 1.3 – ATOMIC THEORY

  2. OBJECTIVES By the end of the lesson you should be able to: • Describe how the atomic theory was developed and who was involved in the process • Draw and describe an atom using 4 major properties

  3. HISTORICAL UNDERSTANDING • Chinese: world was based on 5 elements (earth, water, fire, metal and wood) Balance

  4. HISTORICAL UNDERSTANDING • Greeks: argued that matter could be endlessly divided until reaching the atomos (smallest piece) • We use the word atom today from this origin

  5. HISTORICAL UNDERSTANDING • Aristotle did not agree; he believed • Earth, air, fire, and water! • Nobody challenged the idea again for 2000 years!

  6. Alchemists in the Middle Ages tried to turn common metals into gold - nobody succeeded! • They tried for 1000 years!

  7. ATOMIC THEORY DEVELOPMENT • The Revolution! • John Dalton, J.J. Thomson, Ernest Rutherford and Niels Bohr all played a very important part in the development of the atomic theory

  8. JOHN DALTON (1766 – 1844) Dalton’s Atomic Theory: • All matter is made up of small particles called atoms • Atoms cannot be created, destroyed or divided into smaller particles • All atoms of the same element are identical in mass and size but they are different in mass and size from atoms of other elements • Compounds are created when atoms of different elements link together in definite proportions

  9. JOHN DALTON (1766 – 1844)

  10. J.J. THOMSON (1856 – 1940) • Used electric currents in gas discharge tubes to determine that currents were negative charges • Found all substances could produce these currents so all substances had negative charges • Atoms therefore had smaller negative charges which he called electrons

  11. J.J. THOMSON (1856 – 1940) • Proposed the “Raisin Bun Model” which was a positively charged bun with negatively charged raisins in it

  12. ERNEST RUTHERFORD (1871 – 1937) • Student of J.J. Thomson • Shot positive (alpha) particles at a piece of gold foil and saw that some bounced off while most went straight through • Discovered nucleus of an atom (dense positively charged centre of an atom) • Nucleus is made of positive charges and neutral charges

  13. Rutherford Video Explained

  14. NIELS BOHR (1885 – 1962) • Worked under Rutherford and knew that around the nucleus were negative charges • Found that gases would glow if an electric current passes through them (i.e. Neon signs) • Negative charges have certain amount of energy

  15. A REVOLUTION

  16. ATOMIC STRUCTURE • Atom: smallest part of an element that keeps the properties of the element • Is made up of 3 smaller sub-atomic particles • Protons • Neutrons • Electrons

  17. SUB-ATOMIC PARTICLES

  18. Draw an atom! Include the 3 sub-atomic particles in the correct locations (part of nucleus, around nucleus) and their charge (positive, neutral, negative) • Be sure to clearly label your drawing!

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