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To learn how mass spectrometry differentiates between different isotopes of an element, open the Mass Spectrometer Learning Tool and work through the following steps.

  • Under the 'Options' menu, hover over the 'Select Elements' submenu, and select 'chlorine'.
  • Leave the isotope ratios at the default settings (these are the ratios that are commonly found in nature) and click scan.
  • When the scan is complete, click 'spectrum' (along the bottom). Note the very large peak at an m/z ratio of 35, which corresponds to the chlorine-35 isotope. The smaller peak at an m/z ratio of 37 corresponds to the chlorine-37 isotope.
  • Click and drag the mouse over any area of the spectra you would like to zoom in on.
Your turn

Mass spectrometry measures which of the following?

  1. the mass of a sample of neutral atoms
  2. the mass-to-charge ratio of a sample of neutral atoms
  3. the mass of a sample of cations
  4. mass-to-charge ratio of a sample of cations
Click here to show answer
The correct answer is D.

A mass spectrum for a sample of a given element shows only one peak. How many isotopes of that element were present in the sample?

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The mass spectrum only displayed one peak, so there was only one isotope of that element present in the sample.
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