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Chemistry LibreTexts

12.1.1.2: Stronium isotopes treat bone cancer pain

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    236485
  • The element strontium (Sr) is right underneath calcium (Ca) on the periodic table, which means that they tend to have similar chemical behavior and Sr can easily bind to bones in the same places Ca would. This can be useful—Sr is used in Sensodyne toothpaste to minimize tooth sensitivity and 89Sr (isotopic mass = 88.907 g/mol) is used to treat pain in bone cancer patients. The radioactive 90Sr (isotopic mass = 89.908 g/mol) released by the Chernobyl disaster, however, is extremely dangerous for this same reason.

    1. Use the following information about the 3 naturally occurring isotopes of Sr to calculate its average atomic mass. Does your calculation match that on the periodic table? Why are we calculating the average atomic mass using only these three isotopes when we mentioned above that 89Sr and 90Sr exist?

       

      Isotope

       

       

      Isotopic abundance (%)

       

       

      Isotopic mass (g/mol)

       

       

      86Sr

       

       

      ?

       

       

      85.90926

       

       

      87Sr

       

       

      7.00%

       

       

      86.90888

       

       

      88Sr

       

       

      82.58%

       

       

      87.90561

       

       

       

    2. I would like to know how many moles of 89Sr are administered to a cancer patient who weighs 16 kg. A radiation dose of 1.5 MBq/kg of body mass using 89Sr will decrease pain in 80% of bone cancer patients without significant toxicity. Note that Bq are a unit of radiation and MBq is “mega” Bq. 89Sr is delivered as a drug called MetastronTM that delivers 37 MBq/mL. Each mL of Metastron contains 15 mg of the drug, which is 55% 89Sr by mass.

    Solutions

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