Copper has two isotopes, copper-63 and copper-65. The relative abun-

dance of copper-63 is 69.1% and copper-65, 30.9%. Calculate the

average atomic mass of copper.

63.55 amu

Explanation:

(0.692 * 62.930) + (0.308 * 64.928) = 63.55 amu

Copper has two naturally occurring

isotopes: copper-63 (69.17%) and

copper-65 (30.83%).

Calculate the average atomic mass of

copper if the relative masses of the

isotope are copper 63 (62.93 amu)

and copper-65 (64.93 amu).

Cu-63 (0.6917 x 62.93 amu)

Cu-65 + (0.3083 x 64.93 amu)

Avg. mass = 63.55 amu