<span>To find the number of atoms, you must first find the number of moles. If 238U is 238.029g/mol, and we have 1.75 grams, how many moles is that? 1.75 divided by 238.029 = 0.007352045 moles. To find the number of atoms in 0.007352045 moles, you multiply by a mole: </span> <span>0.007352045 x 6.02 x 10^23 = 4.426 x10^21 atoms. </span>
<span>Same procedure for 206Pb: </span> <span>4.59 divided by 205.97446 = 0.022284316 moles </span> <span>0.022284316 x 6.02 x 10^23 = 1.342 x10^22 atoms. </span>
<span>Hope that helps you! https://answers.yahoo.com/question/index?qid=20100331153014AAoMXcu </span>