# If an Atom was the size of a grain of salt...

by Embison
Tags: atom, grain, salt, size
 P: 49 What object would represent the size of a grain of salt at this scale? Would it be bigger than Earth?
Mentor
P: 19,758
 Quote by Embison What object would represent the size of a grain of salt at this scale? Would it be bigger than Earth?
Is this a homework problem?

What are your thoughts on your problem?
 Mentor P: 5,227 The smallest atom is helium at ~30pm, a very large atom like caesium is ~225pm. Salt obviously varies in size but let's say it's particularly fine at 100μm then a helium atom is ~3 millionth of the size and a caesium atom is ~0.5 millionth of the size. So if a helium atom was as large as a grain of salt a grain of salt would be ~100m wide and for a caesium atom it would be ~16m wide. I'm pretty sure my math is correct there
P: 49

## If an Atom was the size of a grain of salt...

No. I'm reading this...

http://nextbigfuture.com/2012/02/sin...rfect.html?m=1

and I'm curious about how small that really is.
 P: 280 If I remember correctly, an atom is roughly in the 10^-11 - 10^-10 scale, and an average grain of salt could have a diameter of, let's say, 10^-3 m (assuming it's a sphere). This leaves you with a diameter ratio of about 50 million.
 P: 49 So what object would represent the size of the grain of salt?
Mentor
P: 5,227
 Quote by Embison So what object would represent the size of the grain of salt?
See my post #3 above.
 P: 49 I did but you didnt mention any objects.
Mentor
P: 5,227
 Quote by Embison I did but you didnt mention any objects.
16 metres long is roughly five cars. 100 metres long is roughly the width of the international space station. That's obviously just length so use your imagination to make it 3d.
Mentor
P: 19,758
 Quote by Ryan_m_b The smallest atom is helium at ~30pm
A hydrogen would be a bit smaller, being a single proton.
 P: 49 Thanks Ryan. I wasnt sure if you meant miles or meters. Is it possible to estimate which atomic scale that transistor was manufactured at from the link I posted? And what size would a grain of salt represent from my original question compared to the size of that transistor? Thank you for any help!!
 P: 124 Mark44, you may wish to double check that. It's been a while since my chem prof explained this to me, but I believe the additional proton in helium makes it smaller, especially since both electrons are in the same shell. http://chemwiki.ucdavis.edu/Inorgani..._Atomic_Radius
Mentor
P: 5,227
 Quote by Embison Thanks Ryan. I wasnt sure if you meant miles or meters. Is it possible to estimate which atomic scale that transistor was manufactured at from the link I posted? And what size would a grain of salt represent from my original question compared to the size of that transistor? Thank you for any help!!
Well the atom they mention is phosphorous which is roughly 180pm in size (note that atom "size" can vary based on how they bond IIRC).

Taking a grain of salt to be 100μm in size: 100000000pm/180pm = 555555.55
100μm*555555.55 = 55555555μm = 55555.555mm = 55.555555m

So a grain of salt would be ~half the size of a 100m sprint track.

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