Copper on periodic table:63.546 Explain how you know that this value cannot be the mass of just one copper atom (but instead the average of two or more isotopes). HELP?

In nature, copper appears in many different . These isotopes appear in many different frequencies and masses.

On , the value given for copper represents the weighted average of all the masses of all the isotopes of copper. In this instance, there are 2 isotopes of copper: ##_^63CU## and ##_^65CU##. ^63CU appeares in nature at a frequency of 69.17%, and ^65CU appears at frequency of 30.83%. To find the mass given on the periodic table, you do this: (mass of an isotope * percentage in decimal form) + (mass of an isotope * percentage in decimal form), adding any more you need. In this instance, it should look like this:

##(62.93*0.6917)+(64.93*0.3083)##

##43.5287+20.0719##

##63.546## amu