Question

The diameter of a neutral argon atom is about 2.0 ✕ 102 pm. Suppose that we could line up argon atoms side by side in contact with one another. Approximately how many argon atoms would it take to make the distance from end to end 1 cm

Answer 1

$1\ pm=10^{-12}\ m\\1\ cm=10^{-2}\ m\\\\\text{therefore}\ 1\ pm=10^{-10}\ cm\to 1\ cm=10^{10}\ pm\\\\10^{10}:(2\cdot10^{2})=\dfrac{10^{10}}{2\cdot10^2}=0.5\cdot10^{10-2}=0.5\cdot10^8=50,000,000\\\\\text{Answer: 50 millions atoms}$