Chapter #2 Lecture Part 2

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  • Figure 2.13
  • Chapter #2 Lecture Part 2

    1. 1. Atomic Mass <ul><li>Atomic and molecular masses can be measured with great accuracy with a mass spectrometer. </li></ul>
    2. 2. Average Atomic Mass or Atomic Weight <ul><li>Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations. </li></ul><ul><li>Average mass is calculated from the isotopes of an element weighted by their relative abundances. </li></ul>
    3. 3. Periodic Table <ul><li>A systematic catalog of elements. </li></ul>
    4. 4. Periodicity <ul><li>When one looks at the chemical properties of elements, one notices a repeating pattern of reactivities. </li></ul>
    5. 5. Periodic Table <ul><li>The rows on the periodic chart are periods. </li></ul>
    6. 6. Groups
    7. 7. Periodic Table <ul><li>Nonmetals are on the right side of the periodic table (with the exception of H). </li></ul>
    8. 8. Periodic Table <ul><li>Metalloids border the stair-step line (with the exception of Al and Po). </li></ul>
    9. 9. Periodic Table <ul><li>Metals are on the left side of the chart. </li></ul>
    10. 10. Chemical Formulas <ul><li>The subscript to the right of the symbol of an element tells the number of atoms of that element in one molecule of the compound. </li></ul>
    11. 11. Molecular Compounds <ul><li>Molecular compounds are composed of molecules and almost always contain only nonmetals. </li></ul>
    12. 12. Diatomic Molecules <ul><li>These seven elements occur naturally as molecules containing two atoms. </li></ul>
    13. 13. Types of Formulas <ul><li>Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound. </li></ul><ul><li>Molecular formulas give the exact number of atoms of each element in a compound. </li></ul>
    14. 14. Types of Formulas <ul><li>Structural formulas show the order in which atoms are bonded. </li></ul><ul><li>Perspective drawings also show the three-dimensional array of atoms in a compound. </li></ul>
    15. 15. Ions <ul><li>When atoms lose or gain electrons, they become ions. </li></ul><ul><ul><li>Cations are positive and are formed by elements on the left side of the periodic chart. </li></ul></ul><ul><ul><li>Anions are negative and are formed by elements on the right side of the periodic chart. </li></ul></ul>
    16. 16. Ionic Bonds <ul><li>Ionic compounds (such as NaCl) are generally formed between metals and nonmetals. </li></ul>

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