The mass of a single lead atom is 3.44×10-22 grams. How many lead atoms would there be in 85.9 milligrams of lead?

2.49×10²⁰ atoms of Pb

Explanation:

This a problen that can be solved with a rule of three:

1 atom of Pb weighs 3.44×10⁻²² g

Let's convert the mass from mg to g → 85.9 mg . 1g / 1000mg = 0.0859 g

Now, the rule of three:

3.44×10⁻²² g is the weight for 1 atom

0.0859 g is the weight for ( 0.0859 g . 1) / 3.44×10⁻²² g = 2.49×10²⁰ atoms of Pb