1.17: Be Able to Calculate the Relative Atomic Mass of an Element (Ar) from Isotopic Abundances

ISOTOPES: Atoms of the same Element that contains the same Atomic Number but different Mass Number

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EQUATION:

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(% of Isotope 1 x Mass of Isotope 1 ) + ( % of Isotope 2 x Mass of Isotope 2) Ar =   _______________________________________________________________                                                                      100

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Example:

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The Table Shows Information about the Isotopes in a sample of Rubidium ISOTOPE NUMBER OF PROTONS NUMBER OF NEUTRONS PERCENTAGE OF ISOTOPE IN SAMPLE 1 37 48 72 2 37 50 28       Use information from the table to calculate the Relative Atomic Mass of        this Sample of Rubidium. Give your answer to one decimal place     (   72   x   85   )   +   (   28   x   87   )     ____________________________     =   85.6                              100     Relative Atomic Mass = 85.6