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Free protons of high energy and velocity make up 90% of cosmic rays, which propagate through the interstellar medium. [33] Free protons are emitted directly from atomic nuclei in some rare types of radioactive decay. [34] Protons also result (along with electrons and antineutrinos) from the radioactive decay of free neutrons, which are unstable ...
During the 1920s, some writers defined the atomic number as being the number of "excess protons" in a nucleus. Before the discovery of the neutron, scientists believed that the atomic nucleus contained a number of "nuclear electrons" which cancelled out the positive charge of some of its protons. This explained why the atomic weights of most ...
Between about 2 and 20 minutes after the Big Bang nuclear fusion reactions convert a 1/7 mixture of neutrons and protons in to a mix of protons, deuterium (a proton fused with a neutron), 3 He, 4 He, with trace amounts of 7 Li and 7 Be. These reactions end when the temperature falls below the 0.07MeV needed for nuclear fusion.
When 14 N was proposed to consist of 3 pairs each of protons and neutrons, with an additional unpaired neutron and proton each contributing a spin of 1 ⁄ 2 ħ in the same direction for a total spin of 1 ħ, the model became viable. [70] [71] [72] Soon, neutrons were used to naturally explain spin differences in many different nuclides in the ...
1897 J. J. Thomson discovered the electron; 1897 Emil Wiechert, Walter Kaufmann and J.J. Thomson discover the electron; 1898 Marie and Pierre Curie discovered the existence of the radioactive elements radium and polonium in their research of pitchblende; 1898 William Ramsay and Morris Travers discover neon, and negatively charged beta particles
The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count.
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A model of an atomic nucleus showing it as a compact bundle of gluonss (red, blue&yellow) and electronss (white), the two types of nucleons.In this diagram, protons and neutrons look like little balls not stuck together, but an actual nucleus (as understood by modern nuclear physics) cannot be explained like this, but only by using quantum mechanics.