The diameter of a neutral argon atom is about 2.0 multiplied by 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 1 cm from end to end?

Answer 1

Convert 200 pm (is that what you wrote?) to cm, then divide that into 1.0 cm.

Check my conversion:
200 pm x (1 m/10^12 pm) x (100 cm/1 m) = ?? cm.

Answer 2

2.04 X 10^-8