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Atomic structure


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Notes for chapter 4

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Atomic structure

  1. 1. Atomic Structure<br />Defining the Atom<br />
  2. 2. Opening<br />What are we going to learn today?<br />Essential Questions: <br />How did Democritus describe atoms?<br />How did John Dalton further Democritus’s ideas on atoms?<br />What instruments are used to observe individual atoms?<br />GPS Standards:<br />SCSh1b – Recognize that different explanations can be given for the same information<br />SCSh7c – Understand how major shifts in scientific knowledge occur.<br />SCSh7d – Hypotheses often cause scientists to develop new experiments that produce additional data.<br />SCSh7e – Testing, revising and occasionally rejecting new and old theories never ends.<br />
  3. 3. Why are we doing this? (logbook)<br />What are some objects that require experimental data in order to “picture” them, either because they are small or inaccessible?<br />Here’s how. (agenda)<br />Discuss early models of the atom<br />Begin gathering information for an atomic theory timeline.<br />Complete Section Review WS<br />Wrap-up<br />Evaluate and criticize the following statements:<br />“All atoms are identical.”<br />Chemical reactions occur when atoms of one element change into atoms of another element.”<br />
  4. 4. Early Models of the atom<br />atom<br />Smallest particle of an element that retains its identity in a chemical reaction<br />Democritus (460BC – 370BC)<br />Greek philosopher<br />One of the first to suggest the existence of atoms<br />Believed that atoms were indivisible and indestructible<br />No attempt to explain chemical behavior<br />No experimental support<br />
  5. 5. John Dalton (1766 – 1844)<br />English chemist and schoolteacher<br />Dalton’s atomic theory<br />All elements are composed of tiny indivisible particles called atoms.<br />Atoms of the same element are identical. The atoms of any one element are different from those of any other element.<br />Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.<br />Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.<br />
  6. 6. Sizing up atoms<br />Pure copper penny contains about 2.4x1022 atoms of copper<br />6x109 people on Earth<br />Radius of most atoms is between 5x10-11m and 2x10-10m.<br />Individual atoms can only be observed by scanning tunneling electron microscope<br />
  7. 7. Scanning tunneling electron microscope<br />
  8. 8. SCE Microscope depiction of electron cloud<br />
  9. 9. Diagram of scanning tunneling electron microscope<br />
  10. 10. Quantum forest<br />
  11. 11. Opening – 8/29/11<br />What are we going to learn today?<br />GPS Standards<br />SCSh1b – Recognize that different explanations can be given for the same information<br />SCSh1c – Explain that further understanding of scientific problems relies on the design and execution of new experiments which may reinforce or weaken opposing explanations.<br />SCSh7c – Understand how major shifts in scientific knowledge occur.<br />SCSh7d – Hypotheses often cause scientists to develop new experiments that produce additional data.<br />SCSh7e – Testing, revising and occasionally rejecting new and old theories never ends.<br />SC3a – Discriminate between the relative size, charge, and position of protons, neutrons, and electrons in the atom.<br />
  12. 12. Why are we doing this? <br />Essential Questions <br />What are 3 kinds of subatomic particles?<br />How can you describe the structure of the nuclear atom?<br />Here’s how. (agenda)<br />Notes/discussion about the discovery of protons, neutrons, and electrons<br />Students work in pairs to complete a chart about the three subatomic particles.<br />Complete Section 4.2 Review Sheet<br />
  13. 13. Subatomic particles<br />Three kinds of subatomic particles<br />Proton<br />Positive charge<br />Neutron<br />No charge<br />Electron<br />Negative charge <br />
  14. 14. Discovery of the electron<br />J.J. Thomson (1856 – 1940)<br />Discovered the electron in 1897<br />Cathode ray tube experiments<br />Hypothesized that cathode rays are tiny negatively charged particles moving at high speed (electrons)<br />Measured the charge to <br /> mass ratio of the electron<br />Plum Pudding Model<br />
  15. 15. Cathode ray deflected by a magnet<br />Plum Pudding Model<br />
  16. 16. Robert Millikan (1868 – 1953)<br />determined the quantity of charge on an electron<br />Used Thomson’s charge-mass ratio to calculate the mass of the electron (1916)<br />Oil drop experiments<br />
  17. 17. Millikan oil drop experiment<br />
  18. 18. Discovery of the proton<br />Eugen Goldstein (1850 – 1930)<br />Found rays traveling in the direction opposite to that of the cathode rays in a cathode ray tube<br />Called these rays canal rays (later renamed protons)<br />
  19. 19. Discovery of the Neutron<br />James Chadwick (1891 – 1974)<br />Discovered the neutron (1932)<br />
  20. 20. Properties of subatomic particles<br />
  21. 21. Discovery of the Nucleus<br />Ernest Rutherford (1871 – 1937)<br />Gold foil experiments (1911)<br />Findings<br />Atom is mostly empty space<br />Small positively charged <br /> nucleus<br />Electrons move around <br /> outside the nucleus<br />Nuclear model<br />
  22. 22. Explanation of results of gold foil experiment<br />
  23. 23. Comparison of Thomson’s plum pudding model (top) and Rutherford’s nuclear model (bottom) <br />Notice that the nucleus in this model is solid. Protons and neutrons had not been discovered.<br />
  24. 24. Ticket out the door<br />Write a paragraph explaining how Rutherford’s gold foil experiment yielded new evidence about atomic structure. Hint: First describe the setup of the experiment. The explain how Rutherford interpreted his experimental data.<br />
  25. 25. Opening<br />Essential Questions: <br />What makes one element different from another?<br />How do you find the number of neutrons in an atom?<br />How do isotopes of an element differ?<br />How do you calculate the atomic mass of an element?<br />Why is the periodic table useful?<br />GPS Standards:<br />SC3c – Explain the relationship of the proton number to the element’s identity.<br />SC3d – Explain the relationship of isotopes to the relative abundance of atoms of a particular element.<br />
  26. 26. Atomic Number<br />The number of protons in an atom identifies the element.<br />Atomic number<br />the number of protons in the nucleus of an atom<br />Each element has a unique atomic number<br />Because atoms are neutral, the number of electrons(-1) must equal the number of protons(+1).<br />
  27. 27. Sample Problem p. 111<br />How many protons and electron are in each of the following atoms?<br />Fluorine<br />Calcium<br />Aluminum<br />
  28. 28. Mass Number<br />Mass number <br />Total number of protons and neutrons in the nucleus of the atom<br /># neutrons = mass number – atomic number<br />
  29. 29. Hyphen notation<br />Name of element followed by a hyphen and the mass number<br />Examples <br />Carbon – 12<br />Carbon – 14<br />Oxygen – 18<br />
  30. 30. Nuclear Notation<br />The symbol of the element<br />Mass number as a superscript before the symbol<br />Atomic number as a subscript before the symbol<br />
  31. 31. isotopes<br />Isotopes <br />atoms of the same element that have different masses<br />Atoms that have the same number of protons but different numbers of neutrons<br />Atoms that have the same atomic number but different mass numbers<br />
  32. 32. Isotopes of hydrogen<br />Protium<br />Hydrogen – 1<br />Deuterium<br />Hydrogen – 2<br />Tritium<br />Hydrogen – 3<br />
  33. 33. Atomic mass<br />Atomic mass unit (amu)<br />1/12 the mass of a carbon-12 atom<br />Mass of a single proton or neutron is approximately 1amu<br />Atomic mass<br /> weighted average mass (in amu) of the atoms in a naturally occurring sample of an element<br />Mass shown on the periodic table<br />
  34. 34. Calculating Atomic mass<br />Atomic mass = [(relative abundance)(atomic mass of the isotope)] for each naturally occurring isotope<br />Multiply the relative abundances (expressed as a decimal) times the mass of each isotope then add the results<br />
  35. 35. Sample problem, p. 117<br />Atomic mass = 1.993 amu + 8.817 amu = 10.81 amu<br />
  36. 36. Periodic Table Preview<br />Periodic table – an arrangement of elements in which the elements are separated into groups based on a set of repeating properties<br />Period <br />Horizontal row on the Periodic Table<br />7 periods<br />Properties vary as you move across a period<br />Group or family<br />Vertical column of the Periodic Table<br />18 groups<br />Elements within a group have similar properties<br />