The radius of a barium atom is 217 pm. How many barium atoms would have to be laid side by side to span a distance of 4.33 mm?

Answer 1

All right, you've got the radius of an atom. Whenever you get a problem asking for the volume, density, etc. you assume the atom is a sphere. The diameter of a barium atom would then be:

217pm * 2 = 434pm

Either convert 4.33mm to pm or 434pm to mm. I'll convert 4.33mm to pm:

4.33mm * 1.0*10^9pm/1mm = 4.33 * 10^9pm

So how many atoms with a diameter of 434pm fit in 4.33 * 10^9pm?

4.33 * 10^9pm * 1 Ba atom/434pm = 9976959 Ba atoms