Question 5.3: Suppose that we have been able to obtain 10 g of pure natura......

From Appendix D, there are 19.1 g of pure uranium per cubic centimeter. So 10 g of pure uranium is equivalent to a volume of only 10/19.1 = 0.523 cm³. From Appendix D, we also know that 1 cm³ of pure uranium has 4.833 × 10^{22} atoms in it. So 0.523 cm³ of pure uranium must therefore contain 0.523 × 4.833 × 10^{22} = 2.530 × 10^{22} atoms of uranium.