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At the atomic level, at sea level on earth, what percentage of normal pure drinking water is void or empty space? What percentage of lead (the kind used to insulate from nuclear radiation) is void or empty space?

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up vote 2 down vote accepted

I'm guessing that you're asking this because you've heard that atoms are mostly empty space. The trouble is that your question doesn't have an answer because how much empty space you think there is in an atom depends on how hard you're willing to press on the atom.

As chance would have it, I've just answere a question that deals with exactly this question in a different context: How can black holes be so dense?

If you take water and compress it really really hard you can compress it until the nuclei at the centre of the atoms are touching, and at this point the density is about $10^{18}$ kg/m$^3$. Since water normally has a density of $10^{3}$ kg/m$^3$ the compression factor is $10^{15}$, so by this standard an atom is 99.9999999999999% empty space. The trouble is that if you squeeze it even harder you'll find you can squeeze the nuclei into each other and increase the density still further. In fact squeeze hard enough and the atom will turn into a singularity with zero volume. So we'd have to conclude that an atom is 100% empty space.

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