Assume you have 60 micrograms (1 microgram = 10-6 gram) of pure u-238. how many nuclei n0 is this? (recall avogadro's number equals 6.022×1023 particles per mole.)

Atomic mass of Uranium is 238.

Hence, 1 mole = 238 g of Uranium will have 6.022×10^23 of Uranium nuclei.

∴, 60 X 10^-6 g of Uranium will have = 1.518 X 10^17 nuclei of Uranium.

It was ernest rutherford