The element copper has naturally occurring isotopes with mass numbers of 63 and 65. The relative abundance and atomic masses are 69.2% for a mass of 62.93 amu and 30.8% for a mass of 64.93 amu. What is the average atomic mass of copper?

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The element copper has naturally occurring isotopes with mass numbers of 63 and 65. The relative abundance and atomic masses are 69.2% for a mass of 62.93 amu and 30.8% for a mass of 64.93 amu. What is the average atomic mass of copper?

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Answer 1 · 2015-12-30T10:28:33

Take the weighted average of the individual isotopes.

Explanation:

#""^63Cu# has #69.2%# abundance.

#""^65Cu# has #30.8%# abundance.

So, the weighted average is #62.93xx69.2%# #+# #64.93xx30.8%# #=# #63.55# #"amu"#.

If we look at the Periodic Table, copper metal (a mixture of isotopes but #""^63Cu# and #""^65Cu# predominate) has an approximate atomic mass of #63.55# #g*mol^-1#, so we know we are right.

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The element copper has naturally occurring isotopes with mass numbers of 63 and 65. The relative abundance and atomic masses are 69.2% for a mass of 62.93 amu and 30.8% for a mass of 64.93 amu. What is the average atomic mass of copper?

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