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We know atoms are mostly "made" out of empty space, so the nucleus and all the subatomic particle are very small in compared to the magnitude of the atoms. We also know that atoms are incredibly small, so how small are subatomic particle? Can we measure their size?

Is it meaningful to even ask this question?

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    $\begingroup$ "We know atoms are mostly "made" out of empty space" ::grumble:: That statement may be suitable for pop-sci contexts but it is more wrong than right. $\endgroup$ – dmckee Apr 16 '15 at 0:39
  • $\begingroup$ Related: physics.stackexchange.com/q/41676/2451 and links therein. $\endgroup$ – Qmechanic Jun 6 '15 at 11:06
  • $\begingroup$ I have written elsewhere about my take on how "size" works in quantum mechanics. The short answer is that the best "size" is probably the wavelength. $\endgroup$ – rob Jun 7 '15 at 19:22
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In physics, fundamental particles are typically treated as point particles. In this approximation, they have no size or shape whatsoever. They sort of have a location, but we can never exactly pinpoint this location in space, because quantum mechanics tells us that a particle never has an exact location.

The classical model of the electron does yield a non-zero radius, but this model is completely inaccurate when describing the size of the electron. It should not be used in any dimension-related context.

Protons and neutrons (and hadrons) are composite particles, though still subatomic. They do not have a point mass because they are made up of quarks and gluons.

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    $\begingroup$ Note that nucleons are "subatomic" particles and they certainly are not point particles. The word you want is "fundamental". And the classical electron radius has no meaning whatsoever that can be related to the "size" of the particle which is subject to strong experimental upper bounds on order of $10^{-18}\,\mathrm{m}$. $\endgroup$ – dmckee Apr 16 '15 at 0:42
  • $\begingroup$ @dmckee I'll make the changes. I had been thinking of fundamental; you're right. $\endgroup$ – HDE 226868 Apr 16 '15 at 0:42
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Your question is erroneous, there are no "particles", maybe better, "Do subatomic waves have finite size?". Subatomic matter is waves (information) on "______?", with no one point location, they have a length location (anywhere along the wave). The answer is, yes, everything has a finite size. Mostly likely measured in integer planck lengths (1 planck = ‎1.616×10−35 of a metre). Space isn't empty, if it was it couldn't be distorted by gravity.

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  • $\begingroup$ Well as you might know there is a DUALITY in nature! Sometimes phenomena are explained with photons for example behaving like waves and sometime particles! I am talking about these particles... $\endgroup$ – George Smyridis Aug 24 '17 at 10:58

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