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  1. I know that the strong nuclear force holds quarks together to form protons and neutrons, as long as their color charges add up to white, so then how does the strong force simultaneously hold the nucleus (separate protons and neutrons) together without forming a "soup" of all of the separate quarks?

  2. Do groups of quarks which already add up to white work together to bond with other groups that add up to white?

  3. If so, then how do pentaquarks and the hypothetical hexaquark form?

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    $\begingroup$ This is more of a nuclear physics question than chemistry. I flagged it for a move. $\endgroup$ – MaxW Sep 28 '17 at 19:03
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    $\begingroup$ Read about "residual strong force". en.wikipedia.org/wiki/Strong_interaction#Residual_strong_force Pions are exchanged between the protons and neutrons. $\endgroup$ – DavePhD Sep 28 '17 at 19:05
  • $\begingroup$ If I'm not mistaken, @DavePhD's comment holds in general for our understanding of how interactions work in QFT. For some force, there is an exchange of some particle that mediates the force. $\endgroup$ – Zhe Sep 28 '17 at 19:07
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    $\begingroup$ The residual strong force is somewhat similar in concept to the residual electromagnetic force, on which chemistry is based. Electrons are attracted to the nucleus - this is the primary electromagnetic force that makes atoms neutral. While they are neutral, electrons of one atom also are attracted to the nucleus of another atom thus creating a force between neutral atoms to combine into molecules. This is the residual electromagnetic force. The same idea with the strong force, except the residual strong force is mediated by pions instead of gluons. $\endgroup$ – safesphere Sep 28 '17 at 20:00
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    $\begingroup$ It's not even 100% true that a nucleus is not composed of a soup of quarks. It is only an approximation to treat the nucleus as being composed of particles called "protons" and "neutrons." Roughly speaking, the validity of the approximation is measured by the ratio of nuclear excitation energies (~1 MeV) to excitation energies of the three-quark systems (~1 GeV). The approximation is sort of good to 1 part per thousand. $\endgroup$ – Ben Crowell Sep 28 '17 at 22:52

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