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I just recently read about the existence of internuclear forces as the reason for the nucleus to remain 'stable' as in it doesn't separate out into protons and neutrons even though there is electronic repulsion between protons and electronic attraction between an electron and a proton. But I still wasn't able to figure out why or due to what it exists.

Also, I read that the internuclear force acts on a proton-proton pair,proton-neutron pair and a neutron-neutron pair, but then what about Hydrogen, as it contains only one proton, so why does it still have a stable nucleus? And since it's nucleus is just a positive charge and there is just one negative charge at a very small distance, shouldn't the electron be attracted towards the proton(even the shielding effect is negligible) to reduce the potential energy due to the field between the proton and the electron and thus achieve the lowest possible potential energy state?

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  • $\begingroup$ The forces that keep nucleons (protons and neutrons) together are a remnant of the color force that leads to the formation of protons and neutrons out of quarks. The color force is mediated by gluons in as similar way as the electromagnetic force is mediated by photons. You can think of the remnant nuclear force in a similar way as you would think about van der Waals forces between molecules. $\endgroup$
    – CuriousOne
    Jun 4, 2015 at 7:27
  • $\begingroup$ Oh thanks. Also could you please explain the stability of the hydrogen atom then? $\endgroup$
    – Hiten
    Jun 4, 2015 at 7:28
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    $\begingroup$ A proton is a stable nucleon (single neutrons are not) and the electron is attracted to the proton, but it can't "fall in" because of the laws of quantum mechanics that both are subjected to. While the potential energy would decrease with distance, the momentum uncertainty will increase and this will form a total energy minimum at a finite average distance. $\endgroup$
    – CuriousOne
    Jun 4, 2015 at 7:40
  • $\begingroup$ you might profit by looking at the wiki articles en.wikipedia.org/wiki/Nuclear_force and en.wikipedia.org/wiki/Hydrogen_atom $\endgroup$
    – anna v
    Jun 4, 2015 at 7:44

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Intermolecular forces are something else entirely. The nucleus is stable due to something called residual strong nuclear force.

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Neutrons and protons are made of smaller particles called quarks. Quarks bind to each other with a force called strong nuclear force.

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The nucleus is held together by residual strong nuclear force. This is the binding of quarks to other quarks that are not a part of the nucleon that they are in.

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As long as the residual strong force is stronger than the the electric repulsion, the nucleus will be stable.

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Hydrogen atoms are stable because there is nothing to be repelled. The quarks are held together by strong force. At the same time there is no residual strong force in the nucleus (expect in higher isotopes). This doesn't matter because nothing is repelling in the nucleus.

The electron is stable because of its wavefunction. Basically, there is an equation called the Schrodinger equation that we can use to tell us where a particle might be at a given time. This leads to the construction of the Schrodinger model of the atom.

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The electron doesn't fall in because its wavefunction usually doesn't have it fall in. The electron will usually be where the dots are the densest.

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  • $\begingroup$ maybe you should add that the electron is in a stable quantum mechanical orbital? $\endgroup$
    – anna v
    Jun 4, 2015 at 8:02
  • $\begingroup$ @annav He only asked about the nucleus, but I will probably add that in. $\endgroup$
    – Jimmy360
    Jun 4, 2015 at 8:02
  • $\begingroup$ in his last sentence there is the electron $\endgroup$
    – anna v
    Jun 4, 2015 at 8:03
  • $\begingroup$ @annav My apologizes, I did not see that :D $\endgroup$
    – Jimmy360
    Jun 4, 2015 at 8:06
  • $\begingroup$ fine, a good answer $\endgroup$
    – anna v
    Jun 4, 2015 at 8:54

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