Question

the diameter of a helium atom is about 1*10^2pm.suppose that we could line up helium atoms side by side in contact with one another. aproximately how maney atoms would it take to make the distance from end to end 1cm ?

Answer 1

100 pm = 1E-8 cm = diameter.
# atoms x (2E-8 cm/1 atom) = 1 cm.
Solve for # atoms.