1. Find the average atomic mass of chlorine (Cl).
     
    Symbol Mass number Exact mass Percent abundance
      35 34.968852 75.77
      37 36.965903 24.23
  2. Find the average atomic mass of nitrogen (N).
    Symbol Mass number Exact mass Percent abundance
      14 14.003074 99.63
      15 15.000108 0.37
  3. Find the average atomic mass of silicon (Si).
     
    Symbol Mass number Exact mass Percent abundance
      28 27.976927 92.23
      29 28.976495 4.67
      30 29.973770 3.10
  4. Find the average atomic mass of magnesium (Mg).
    Symbol Mass number Exact mass Percent abundance
      24 23.985042 78.99
      25 24.985837 10.00
      26 25.982593 11.01
  5. Find the average atomic mass of chromium (Cr).
    Symbol Mass number Exact mass Percent abundance
      50 49.946049 4.345
      52 51.940511 83.789
      53 52.940653 9.501
      54 53.938884 2.365
  6. Find the average atomic mass of molybdenum (Mo).
    Symbol Mass number Exact mass Percent abundance
      92 91.906808 14.84
      94 93.905085 9.25
      95 94.905840 15.92
      96 95.904678 16.68
      97 96.906020 9.55
      98 97.905406 24.13
      100 99.907477 9.63
  7. An element “X” has five major isotopes, which are listed below along with their abundances. Calculate the average atomic mass. What is the element?
    Symbol Exact mass Percent abundance
    46X 45.95269 8.00
    47X 46.951764 7.30
    48X 47.947947 73.80
    49X 48.947841 5.50
    50X 49.944792 5.40

     

  1. The isotopes of oxygen are16 8O,17 8O, and18 8O. Oxygen-18 is particularly important because of its use in medicine as a precursor for fluorine-18 (used is Positron Emission Tomography, PET) and as a marker of temperature in studies of earlier climates on the Earth. Find the exact mass of this isotope using the following information:
    Symbol Mass number Exact mass Percent abundance
    16 8O 16 15.994915 99.757
    17 8O 17 16.999132 0.038
    18 8O 18   0.205