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I am trying to come up with everyday size objects comparisions of atomic scales items, e.g. if a proton probability cloud was of size basketball how far would the next atoms to it be?

reason being is to give an idea of the space in between the atoms and giving student some idea of relative atomic object sizes.

Looking for examples of how does dnsity of materials can be reflected in this comparsion scheme, for example comapring a dense material to a relatively far less dense material and much closer the basketball sized atomic cloulds would relatively be closer to each other.

PS : No models of everyday objects as analogy to atomic structure will be used, only relative distances of the structures is the main objective.

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The ratio of sizes between the proton and the atomic cloud is 1:100,000. You can figure out the rest. –  Ron Maimon Aug 28 '11 at 20:54
    
@Ron : Numbers are good, but what in real life can be used to convey the ratio of 1:100,000 ? David's sunflower kernel and footbal field helps more to visualisiations than 1:100,000. –  Arjang Aug 28 '11 at 20:59
    
Yes, but this can be figured out with a ruler and a hand calculator. Why should we have questions whose answer is so mechanical to produce? –  Ron Maimon Aug 28 '11 at 21:17
    
@Ron : What is a mechanical procedure? The simul of sunflower Kernel and Footbal Field? can you use the mechanical precudure to give few more examples that fit this the scale of 1:100000 please? thank you –  Arjang Aug 28 '11 at 23:29
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It's easy enough to look up the sizes of a proton and a typical atom and determine their ratio, then you can use that to compare to real-world objects. For example, hydrogen has a nucleus consisting of a single proton. The radius of the proton is about $1\text{ fm}$, and that of the electron cloud in a hydrogen atom is about $25\text{ pm}$ (though there are some subtleties in the definition of "radius," which I won't go into here). Thus the hydrogen atom is about 25000 times the size of the proton. So if you're using a basketball, with a $24\text{ cm}$ diameter, to represent the proton, the electron cloud would be represented by something 25000 times larger, or about $6\text{ km}$ across - probably the size of a small town.

One comparison that I've often heard is a kernel of corn to a football field. A kernel of corn is typically about $5-7\text{ mm}$ across (by my estimation), whereas a football field at 100 yards is about 13000 times larger. That's not actually the right ratio for a hydrogen atom, but it does give a sense of the huge scale difference involved.

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