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  1. Development of the Atomic Model Ethil L. Carbo Labogon national High School
  2. Development of the Atomic Model
  3. Objectives: describe different models of the atom; draw a diagrammatic model of an atom to explain their understanding about the different atomic models; explain how the atomic models help in understanding the concept of an atom.
  4. What is matter to you? What is matter made of?
  5. Get a strip of paper. Cut the paper in half. Take one of the halves and cut it into half. Continue this process and until you no longer able to cut in half, keep count of how many times the paper has been cut. How many times did you able to cut the strip of paper?
  6. Cut 1 14.0 cm 5.5" Child's hand, pockets Cut 2 7.0 cm 2.75" Fingers, ears, toes Cut 3 3.5 cm 1.38" Watch, mushroom, eye Cut 4 1.75 cm 0.69" Keyboard keys, rings, insects Cut 6 0.44 cm 0.17" Black pepper seeds Cut 8 1 mm 0.04" Thread Congratulations if you’re still in! Cut 10 0.25 mm 0.01" Still cutting? Most have quit by now Cut 12 0.06 mm 0.002" Microscopic range, human hair Cut 14 0.015 mm 0.006" Width of paper, microchip components Cut 18 1 micron 0.0004" Water purification openings, bacteria Cut 19 0.5 micron 0.000018" Visible light waves Cut 24 0.015 micron 0.0000006" Electron microscope range, membranes Cut 31 0.0001 micron 0.0000000045" The size of an Atom!
  7. Have you ever wondered how the atom looks like?
  8. Activity 1.Divide the class into 5 groups according to their name tag color. 2.Draw your own diagrammatic model of an atom in a long bond paper. 3. Rank the models as best, better, and good. 4. Choose a representative from your group to share your ideas on the way you rank the models?
  9. Guide Questions: 1. What criteria did you use to make your ranking? 2. Why did you choose the way you did? 3.Why do you think the best model is better than the others? 4. Which models did you like least? Why?
  10. Who are these men? Unscramble the letter to reveal the name of these men.
  11. Who are these men? DMEOCIRTUS
  12. Who are these men? DEMOCRITUS
  13. Who are these men? JHNO ALDTON
  14. Who are these men? JOHN DALTON
  15. Who are these men? OHJN JSEPHO TOHMSNO
  16. Who are these men? JOHN JOSEPH THOMSON
  17. Who are these men? NEREST RUTEHRFDOR
  18. Who are these men? ERNEST RUTHERFORD
  19. Who are these men? SLINE ORBH
  20. Who are these men? NEILS BOHR
  21. NEIL BORH ERNEST RUTHERFORD DEMOCRITUS J.J. THOMSON JOHN DALTON In this lesson, we’ll learn about the men whose quests for knowledge about the fundamental nature of the atom.
  22. Democritus 470-380 B.C was a Greek philosopher (470-380 B.C.) who is the father of modern atomic thought. He proposed that matter could NOT be divided into smaller pieces forever, eventually the smallest possible piece would be obtained. This piece would be indivisible.
  23. Democritus 460-380 B.C He believed that matter was made of small, hard, particles, that he called “atomos” meaning “uncuttable.” To Democritus, atoms were small, hard particles that were all made of the same material but were different shapes and sizes. Atoms were infinite in number, always moving and capable of joining together.
  24. This theory was ignored and forgotten for more than 2000 years!
  25. Aristotle 384-322 B.C did not believe in the atomic theory . He doesn’t believe empty space could exist, and he taught so otherwise. He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. He believed all substances were made of small amounts of these four elements of matter.
  26. Aristotle 384-322 B.C Most people followed Aristotle’s idea, causing Democritus’ idea- which was that all substances on Earth were made of small particles called atoms- to be overlooked for about 2,000 years! Aristotle's view was finally proven incorrect, and his teachings are not present in the modern view of the atom.
  27. John Dalton – English (1766 – 1844) In the early 1800s, the English Chemist John Dalton performed a number of experiments that eventually led to the acceptance of the idea of atoms. Marks the beginning of the development of modern atomic theory. Dalton and Democritus are similar Dalton’s research is known as Dalton’s Atomic Theory which was proposed in
  28. Dalton’s Early Atomic Model Suggested that all matter was made up of TINY SPHERES that were able to bounce around with perfect elasticity. • Called them ATOMS He envisioned atoms as solid, hard spheres, like billiard(pool) balls, so he used wooden balls to model them. “Billiard Ball” model
  29. Dalton’s Theory 1. All matter is comprised of tiny, definite particle called atom. Atoms are indivisible and indestructible particles. 2. Atoms of the same element are exactly alike. The atom of one element are different from the atoms of other elements.
  30. Dalton’s Theory 3. Atoms cannot be created or destroyed during a chemical reaction and the atoms of one element cannot change into the atom of another element. 4. Compounds are formed by the joining of atoms of two or more elements. Compounds and reactants contain the same total number of particles.
  31. Dalton’s Theory This theory became one of the foundations of modern chemistry.
  32. But Wait…. Experimental studies of the atom soon showed that it (the atom) was not indivisible… it has smaller parts!
  33. Thomson’s Plum Pudding Model In 1897, the English scientist J.J. Thomson provided the first hint that an atom is made of even smaller particles. Just over 100 years ago, J. J. Thomson discovered that electrons are relatively low mass, negatively charged particles present in atoms.
  34. Thomson’s Plum Pudding Model He discovered it by doing experiment using cathode ray tube. He was the first scientist to show that atom was made of even smaller thing. He proposed a model in which the atom consists of a uniform distribution of positive charge, in which electrons are embedded (like raisins in plum pudding). “The Plum Pudding” Model
  35. Thomson’s Experiment Used the Cathode ray tube to discover electrons
  36. Thomson’s Experiment Voltage source + - Vacuum tube Metal Disks
  37. Thomson’s Experiment Voltage source + -
  38. Thomson’s Experiment Voltage source + -
  39. Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source + -
  40.  Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source + -
  41. Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source + -
  42. Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source + -
  43. Voltage source Thomson’s Experiment By adding an electric field
  44. Voltage source Thomson’s Experiment By adding an electric field + -
  45. Voltage source Thomson’s Experiment + - By adding an electric field
  46. Voltage source Thomson’s Experiment + - By adding an electric field
  47. Voltage source Thomson’s Experiment + - By adding an electric field
  48. Voltage source Thomson’s Experiment Adding an electric field cause the beam to move toward the positive plate. Thomson concluded the beam was made of negative moving pieces. + - -
  49. Thomson’s “Plum Pudding” Atom Model
  50. Using a cathode ray tube, he discovered canal rays which are beams of positively charged particles. He is credited with the discovery of protons in an atom. Canal Rays discovery Eugen Goldstein 1850-1930
  51. Ernest Rutherford- Nuclear Model He continued his teacher, J.J. Thomson’s research. He used alpha ray that shot to atom using gold foil. Rutherford’s experiment showed that atoms have positive particle in the and are mostly an empty space
  52. Ernest Rutherford- Nuclear Model He hypothesis of atom model is “ atom consist of nucleus that has positive charge and surrounding with moving electrons. He discovered the nucleus of a gold atom with his “gold foil” experiment - dense, positive charge in the center of the atom
  53. Using J.J Thomson’s Plum Pudding atomic model, Rutherford predicted the alpha particles would pass straight though the gold foil. That’s not what happened. Rutherford Experiment
  54. most alpha particles go straight through the gold foil A few alpha particles are sharply deflected by very small amounts. A very few get deflected greatly. Even fewer get bounced off the foil and back to the left. Gold Foil Experiment Results
  55. Rutherford’s Conclusion • The atom is mostly empty space. • There is a small, dense center with a positive charge. • The nucleus is approximately 100,000 times smaller than the atom. • Proposed the Nuclear model
  56. Neils Bohr’s Model While the Rutherford model focused on describing the nucleus, Niels Bohr turned his attention to describing the electron. improved Rutherford’s idea by adding that the electrons were in ORBITS. • Proposed that electrons surround the nucleus in specific “ENERGY LEVELS” or “SHELLS. ” • Each orbit only able to contain a SET NUMBER of electrons.
  57. Neils Bohr’s Model He used Hydrogen atom for his experiment and explain about spectrum of it. proposed the planetary model Bohr’s Model
  58. •An atom consists of positively charge nucleus and the electrons revolve around it in special orbits called discrete orbits or energy levels •The energy of these discrete orbits remained fixed. •These energy levels are represented by 1,2,3,4 or K, L, M, N starting from the center Bohr’s Model of atom suggested that:
  59. James Chadwick In 1932, Chadwick observed that beryllium, when exposed to bombardment by alpha particles, released an unknown radiation that in turn ejected protons from the nuclei of various substances. Chadwick interpreted this radiation as being composed of particles of mass approximately equal to that of the proton. These newly discovered particles Chadwick’s Experiment
  60. James Chadwick’s Experiment
  61. Electron Cloud Model Proponents: Schrodinger, Heisenberg, Einstein and many other scientists Thought that the problem with Bohr’s model was restricting the electrons to specific orbits. Schrondinger wondered if electrons might behave like light , which scientist s already knew had properties of both particles and a waves. He speculated that electrons might also travel like a wave.
  62. Electron Cloud Model According to today’s atomic theory, electrons do not orbit the nucleus in neat planet-like orbits but move at high speeds in an electron cloud around the nucleus. In the electron cloud, electrons whirl or moved rapidly around the nucleus billions of times in one second.
  63. Electron Cloud Model The electron cloud model says that we cannot know exactly where an electron is at any given time, but the electrons are more likely to be in specific areas. You can’t specify the exact location of an electrons. However, Schrodinger showed that you can at least determine where an electron is mostly likely to be.
  64. Electron Cloud Model They are not moving around in random patterns; an electron’s location depends upon how much energy the electron has.
  65. Application Redraw a diagrammatic model of your own model of an atom. Answer the following questions below and choose another representative to share views and understanding about the atom to the class.
  66. Guide Questions 1.What does your new drawing show? What does it not show? 2.What features of your atom can you show now that you didn’t show in the first drawing (done before the activity)? 3. What have you learned about atoms that you didn’t know before? 4. Why is there more than one correct way of modelling an atom? 5. What sort of information do you think contributed to the development of new models of atoms?
  67. Who proposed first that matter is composed of tiny, indivisible particles? Democritus Let’s Check Your Understanding
  68. Who was the scientist the first to adapt Democritus’ theory and proposed the first modern Atomic Model? John Dalton
  69. What is Dalton’s atomic model looks like? Billiard Ball
  70. Who proposed the plum pudding model of the atom? J.J. Thomson
  71. Rutherford ‘s model of the atom concentrated on the nucleus. Where did Bohr’s model focused on? Electrons
  72. Assignment Create an Atomic Model Phase book Page- Choose one scientist who contributed the atomic model for you to research. Include the following information: a. Profile Name: (place your scientist’s name) b. Profile Picture: (draw your scientist’s atom) c. Job: (What did the scientist study?) d. Years Active: (What years did the scientist work on the atom?) e. Claim to Fame: (Atomic Theory Discovery/Contribution of this scientist) f. Memories/Analogy: (clue that will help you remember this scientist’s model of the atom)