Suppose that there were two natural isotopes of Copper 80% of the atoms had a mass of 63, and - Science - Structure of the Atom

Question

Suppose that there were two natural isotopes of Copper 80% of
the atoms had a mass of 63, and 20% of the atoms had a mass of 65
What would that average atomic weight of copper be?

Snehil Aggarwal · Accepted Answer

The isotope with atomic mass 63u has mass percentage = 80%
the isotope with atomic mass 65u has mass percentage = 20%
average atomic mass = 63 x 80/100 + 65 x 20/100
= 50 4 + 13
= 63 4u

Suppose that there were two natural isotopes of Copper. 80% of the atoms had a mass of 63, and 20% of the atoms had a mass of 65. What would that average atomic weight of copper be?