Tin has 10 stable isotopes. The heaviest, 124Sn, makes up 5.80% of naturally occurring tin atoms. How many atoms of 124Sn are present in 91.0 g of naturally occurring tin?

Question

Tin has 10 stable isotopes. The heaviest, ¹²⁴Sn, makes up 5.80% of naturally occurring tin atoms.

How many atoms of ¹²⁴Sn are present in 91.0 g of naturally occurring tin?

What is the total mass of the ¹²⁴Sn atoms in this sample?

Answer 1

Dividing 5.80% of the given mass of tin by 124 would give the number of moles of the heaviest isotope.

Since tin is monoatomic (metal), there are that number times Avogadro's number of atoms of the heaviest isotope present.