A model of an atomic nucleus showing it as a compact bundle of protons (red) and neutrons (blue), the two types of nucleons. In this diagram, protons and neutrons look like little balls stuck together, but an actual nucleus (as understood by modern nuclear physics) cannot be explained like this, but only by using quantum mechanics. In a nucleus that occupies a certain energy level (for example, the ground state), each nucleon can be said to occupy a range of locations.
The diameter of the nucleus is in the range of 1.70 fm (1.70×10−15 m[7]) for hydrogen (the diameter of a single proton) to about 11.7 fm for uranium.[8] These dimensions are much smaller than the diameter of the atom itself (nucleus + electron cloud), by a factor of about 26,634 (uranium atomic radius is about 156 pm (156×10−12 m))[9] to about 60,250 (hydrogen atomic radius is about 52.92 pm).[a]
The branch of physics involved with the study and understanding of the atomic nucleus, including its composition and the forces that bind it together, is called nuclear physics.
^Miller, Arthur I., ed. (1995). Early quantum electrodynamics: a source book (1. paperback ed.). Cambridge: Cambridge Univ. Press. pp. 84–88. ISBN978-0-521-56891-3.
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