The problem statement, all variables and given/known data A bar of copper has dimensions 0.5605 ft. x 3.545 in x 5.722 cm. The density of copper is 8.921 g / cm3. Copper contains 2 isotopes, 63Cu (69.09% abundant) and 65Cu (30.91% abundant). How many neutrons are in the bar of copper? The attempt at a solution I took the volume: 11.37cm^3 x 8.921g/cm^3 x 6.022E23 neutrons/63.546g Cu = 9.612E23 neutrons. Is this right? I think I need to use the isotope information somewhere but I don't know where or how.