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  for Metal Finishing since 1989
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Physics Experiments

I have been asked to find the diameter of a copper atom. I think I will need to find the density of material but am unsure of an approach to take. Any help would be useful.

Thank you,

David
- Stowmarket, Suffolk, East Anglia, England
2003

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The "diameter" of an atom can mean different things in different contexts, because atoms are not solid objects that really have a "diameter" in the way a glass marble has a diameter. Still, if someone told you how many marbles of a uniform size fit into a box of such and such dimension, you could determine the diameter of the marbles. And in a similar way, if you know how many atoms of copper fit into a volume of a given size, you can determine their "diameter" as if they were marbles.

Yes, you need to know the density of copper. You also need to know the molecular weight (atomic weight) of copper, and Avagadro's number. I think if you read up on Avagadro's number you will figure out the general idea.

Depending on your grade level, though, another thing you might need to know is whether copper forms a body-centered cubic structure, a face-centered cubic structure, or some other crystal structure. Because, actually, how many marbles will fit in the box depends on how you stack them. (Picture that you've completely filled the bottom layer of the box with marbles; the next marble you drop in will not balance on top of a marble in the bottom layer, it will nestle down between four of them).

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003