Chapter #2 Lecture Part 1


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  • Figure 2.1 John Dalton (1766-1844)
  • Chapter #2 Lecture Part 1

    1. 1. Atomic Theory of Matter <ul><li>The theory that atoms are the fundamental building blocks of matter reemerged in the early 19th century, championed by John Dalton. </li></ul>
    2. 2. Dalton’s Postulates <ul><li>Each element is composed of extremely small particles called atoms. </li></ul>
    3. 3. Dalton’s Postulates <ul><li>All atoms of a given element are identical to one another in mass and other properties, but the atoms of one element are different from the atoms of all other elements. </li></ul>
    4. 4. Isotopes <ul><li>Atoms of the same element with different masses. </li></ul><ul><li>Isotopes have the same number of protons but a different numbers of neutrons. </li></ul>
    5. 5. Dalton’s Postulates <ul><li>Atoms of an element are not changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions. </li></ul>
    6. 6. Law of Conservation of Mass <ul><li>The total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place. </li></ul>
    7. 7. Dalton’s Postulates <ul><li>Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms. </li></ul>
    8. 8. Law of Constant Composition Joseph Proust (1754 – 1826) <ul><li>Also known as the law of definite proportions. </li></ul><ul><li>The elemental composition of a pure substance never varies. </li></ul>
    9. 9. Lecture Problem <ul><li>A pure compound is composed the carbon and oxygen. Given the following data, illustrate the law of definite proportions. </li></ul><ul><ul><li>Sample #1: 1.201 grams carbon & 3.200 grams of oxygen. </li></ul></ul><ul><ul><li>Sample #2: 60.05 grams carbon & 160.00 grams of oxygen </li></ul></ul><ul><ul><li>Sample #3: 27.29% carbon & 72.71% oxygen </li></ul></ul>
    10. 10. Lecture Problem <ul><li>A compound of phosphorus and chlorine used in the manufacture of a flame-retardant treatment for fabrics contains 1.20 grams of phosphorus for every 4.12 grams of chlorine. Suppose a sample of this compound contains 6.22 grams of chlorine, how many grams of phosphorus does it contain? </li></ul>
    11. 11. Law of Multiple Proportions <ul><li>Whenever two elements form more than one compounds, the different masses of one element that combine with a fixed mass of the other element are in ratio of small whole numbers. </li></ul>
    12. 12. Lecture Problem <ul><li>Compound #1: </li></ul><ul><ul><li>6.005 grams carbon & 8.000 grams oxygen. </li></ul></ul><ul><li>Compound #2: </li></ul><ul><ul><li>6.005 grams carbon & 16.000 grams oxygen. </li></ul></ul>
    13. 13. Lecture Problem <ul><li>Two different compounds of made of phosphorus and chlorine exist. One compound consist of 6.194 grams of phosphorus and 21.27 grams of chlorine. The second compound consist of 2.32 grams of phosphorus and 13.29 grams of chlorine. Illustrate the law of definite proportions. </li></ul>
    14. 14. The Electron <ul><li>Streams of negatively charged particles were found to emanate from cathode tubes. </li></ul><ul><li>J. J. Thompson is credited with their discovery (1897). </li></ul>
    15. 15. The Electron <ul><li>Thompson measured the charge/mass ratio of the electron to be 1.76  10 8 coulombs/g . </li></ul>
    16. 16. Millikan Oil Drop Experiment <ul><li>Once the charge/mass ratio of the electron was known, determination of either the charge or the mass of an electron would yield the other. </li></ul>
    17. 17. Millikan Oil Drop Experiment <ul><li>Robert Millikan (University of Chicago) determined the charge on the electron in 1909. </li></ul>
    18. 18. Radioactivity <ul><li>The spontaneous emission of radiation by an atom. </li></ul><ul><li>First observed by Henri Becquerel. </li></ul><ul><li>Also studied by Marie and Pierre Curie. </li></ul>
    19. 19. Radioactivity <ul><li>Three types of radiation were discovered by Ernest Rutherford: </li></ul>
    20. 20. The Atom, circa 1900 <ul><li>“ Plum pudding” model, put forward by Thompson. </li></ul><ul><li>Positive sphere of matter with negative electrons imbedded in it. </li></ul>
    21. 21. Discovery of the Nucleus <ul><li>Ernest Rutherford shot  particles at a thin sheet of gold foil and observed the pattern of scatter of the particles. </li></ul>
    22. 22. The Nuclear Atom <ul><li>Since some particles were deflected at large angles, Thompson’s model could not be correct. </li></ul>
    23. 23. The Nuclear Atom <ul><li>Rutherford postulated a very small, dense nucleus with the electrons around the outside of the atom. </li></ul><ul><li>Most of the volume of the atom is empty space. </li></ul>
    24. 24. Other Subatomic Particles <ul><li>Protons were discovered by Rutherford in 1919. </li></ul><ul><li>Neutrons were discovered by James Chadwick in 1932. </li></ul>
    25. 25. Subatomic Particles <ul><li>Protons and electrons are the only particles that have a charge. </li></ul><ul><li>Protons and neutrons have essentially the same mass. </li></ul><ul><li>The mass of an electron is so small we ignore it. </li></ul>
    26. 26. Symbols of Elements
    27. 27. Atomic Number <ul><li>All atoms of the same element have the same number of protons </li></ul>
    28. 28. Mass Number