1. The three stable isotopes of silicon have masses and natural abundances as follows. Calculate the atomic mass.

    28Si27.976927 amu92.23%
    29Si28.976495 amu4.67%
    30Si29.973770 amu3.10%
  2. There are two stable isotopes of bromine. Isotope A has a mass of 78.918336 amu and isotope B has a mass of 80.916289 amu.
    • Determine the natural abundance of the isotopes, and report the answer to three significant figures.

    • Write the symbol for the two isotopes.
  3. There are two naturally occurring isotopes of silver, 107AgAg and 109Ag. The atomic mass of silver is 107.87 amu, with 51.82% of the atoms being 107Ag. The mass of an atom of 107Ag is 106.9 amu. What is the mass, in amu, of an atom of 109Ag.


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    Chemistry Department
    British Columbia Institute of Technology, Burnaby, B.C. Canada.
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