Possible Duplicate:
Protons' repulsion within a nucleus
How positively charged protons remain glued to each other while they should repel each other out of nucleus?
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$\begingroup$ Possible duplicates: physics.stackexchange.com/q/9661/2451 and links therein. $\endgroup$ – Qmechanic♦ Jun 6 '12 at 22:17
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Due to one of the four fundamental interactions known as the strong force which, at the scale involved is roughly two orders of magnitude stronger than electromagnetic interaction which repels the protons.
It is interesting to note that small nuclei have roughly equal number of protons and neutrons while heavy nuclei have excess of neutrons over protons. The reason for this change in the ratio of protons to neutrons is that, unlike electromagnetic interaction, the strong force has very limited range and in heavy nuclei greater separation of protons increases the relative significance of the destabilizing electromagnetic force.
answered Jun 6 '12 at 22:12
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$\begingroup$ strong force between the protons or any other particle is also involved? $\endgroup$ – sanjay Jun 6 '12 at 22:17
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$\begingroup$ Between protons and neutrons. The strong interaction does not discriminate by electric charge. $\endgroup$ – Adam Zalcman Jun 6 '12 at 22:23
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$\begingroup$ "...in heavy nuclei greater separation of protons increases the relative significance of the destabilizing electromagnetic force." Shouldn't there be "...in heavy nuclei greater separation of protons decreases...".Protons further apart should make their EM repulsion less significant. Isn't so? $\endgroup$ – Ufomammut Nov 20 '13 at 12:31
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$\begingroup$ No. Electromagnetic force gets weaker there indeed, but strong force does even more. The upshot is that at a slightly greater distances in heavier nuclei the relative significance of electromagnetic force increases. $\endgroup$ – Adam Zalcman Nov 20 '13 at 17:01
