# A 1/4 inch thick lead sheet is used for protection from medical x-rays. If a single lead atom has a diameter 350 pm, how many atoms thick is the lead sheet?

Jan 14, 2016

$\frac{1}{4}$ $\text{inch}$ $=$ $6.35$ $\times$ ${10}^{-} 3$ $m$.

$1$ $\text{pm}$ $=$ $1$ $\times$ ${10}^{-} 12$ $m$

#### Explanation:

We assume that the lead atoms are close packed. Therefore we divide the sheet thickness by the diameter of of a single lead atom.

$\frac{6.35 \times {10}^{-} 3 \cancel{m}}{350 \times {10}^{-} 12 \cancel{m}}$ $=$ Something large. The difficulty with doing these problems is getting such a large number that intuitively you have no idea how feasible the number is.

PS can you help this gentleman, who has asked a similar question?. There are $454$ $g$ in $1$ $\text{pound}$.