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An up quark has electric charge + + 2 / 3 e, and a down quark has charge − + 1 / 3 e, so the summed electric charges of proton and neutron are +e and 0, respectively. [a] Thus, the neutron has a charge of 0 (zero), and therefore is electrically neutral; indeed, the term "neutron" comes from the fact that a neutron is ...
"Free" neutrons or protons are nucleons that exist independently, free of any nucleus. The free neutron has a mass of 939 565 413.3 eV/c 2, or 939.565 4133 MeV/c 2. This mass is equal to 1.674 927 471 × 10 −27 kg, or 1.008 664 915 88 Da. [4] The neutron has a mean-square radius of about 0.8 × 10 −15 m, or 0.8 fm, [20] and it is a spin-½ ...
Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud. Protons and neutrons are bound together to form a nucleus by the nuclear force. 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 ...
The mass of an atomic nucleus is less than the sum of the individual masses of the free constituent protons and neutrons. The difference in mass can be calculated by the Einstein equation, E = mc 2, where E is the nuclear binding energy, c is the speed of light, and m is the difference in mass. This 'missing mass' is known as the mass defect ...
This energy is stored when the protons and neutrons are bound together by the nuclear force to form a nucleus. The mass of a nucleus is less than the sum total of the individual masses of the protons and neutrons. The difference in masses is known as the mass defect, which can be expressed as an energy equivalent. Energy is released when a ...
The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess, [8] which for 35 Cl is –0.03115. Mass excess should not be confused with mass defect which is the difference between the mass of an atom and its constituent particles (namely protons, neutrons and electrons). There are two reasons for mass ...
The rms charge radius is a measure of the size of an atomic nucleus, particularly the proton distribution. The proton radius is about one femtometre = 10 −15 metre. It can be measured by the scattering of electrons by the nucleus. Relative changes in the mean squared nuclear charge distribution can be precisely measured with atomic spectroscopy.
Most of the mass of a proton or neutron is the result of the strong interaction energy; the individual quarks provide only about 1% of the mass of a proton. At the range of 10 −15 m (1 femtometer , slightly more than the radius of a nucleon ), the strong force is approximately 100 times as strong as electromagnetism , 10 6 times as strong as ...