The element copper cu has two naturally occurring isotopes. 69% of all coopers consist of atom with 34 neutrons, 31% of all samples with 36 neutrons. calculate the average atomic weight of cooper atoms

Answer : Average atomic weight of copper atoms will be 63.62 u. 

Explanation : For calculating average atomic weight for any given atom we use this formula,

m = Σ X % abundance

where, m - avg atomic mass of isotope.
and - mass of isotope

on solving we get, 
m = [63 u X (69/100)] + [65 u X (31/100)] = 63.62 u.

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