1. Determine the element's average atomic mass number using the periodic table of the elements. This will be a number with several decimal places behind it. This value is the average
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How do you calculate percent abundance of an isotope? You find the isotope number and then you calculate that into a fraction and then turn the fraction into a percentage and divide
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To find the average atomic mass, we multiply the mass of the isotope by the percent abundance in decimals (and we add isotopes into our equation depending on how many there are) Also
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To calculate percent change use this formula: Percent Change = New Value  Old Value ' Old Value x 100. That is to say percent change equals the new value minus the old value divided
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