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Atomic Mass & Isotopic Abundance

The element boron consists of two isotopes, 10(superscript), 5(subscript) B and 11(superscript), 5(subscript)B. Their masses, based on the carbon scale, are 10.01 and 11.01, respectively. The abundance of 10(superscript), 5(subscript)B is 20.0% and the abundance of 11(superscript), 5(subscript)B is 80.0%. What is the atomic mass of boron?

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The percentages of multiple isotopes must add up to 100%. Apply the following equation ...