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  2. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    There are two types of quarks in atoms, each having a fractional electric charge. Protons are composed of two up quarks (each with charge + ⁠ 2 / 3 ⁠) and one down quark (with a charge of − ⁠ 1 / 3 ⁠). Neutrons consist of one up quark and two down quarks. This distinction accounts for the difference in mass and charge between the two ...

  3. Nuclear fission - Wikipedia

    en.wikipedia.org/wiki/Nuclear_fission

    A schematic nuclear fission chain reaction. 1. A uranium-235 atom absorbs a neutron and fissions into two new atoms (fission fragments), releasing three new neutrons and some binding energy. 2. One of those neutrons is absorbed by an atom of uranium-238 and does not continue the reaction. Another neutron is simply lost and does not collide with ...

  4. Electron shell - Wikipedia

    en.wikipedia.org/wiki/Electron_shell

    In chemistry and atomic physics, an electron shell may be thought of as an orbit that electrons follow around an atom's nucleus.The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on further and further from the nucleus.

  5. Electron transfer - Wikipedia

    en.wikipedia.org/wiki/Electron_transfer

    Furthermore, theories have been put forward to take into account the effects of vibronic coupling on electron transfer, in particular, the PKS theory of electron transfer. [10] In proteins, ET rates are governed by the bond structures: the electrons, in effect, tunnel through the bonds comprising the chain structure of the proteins.

  6. Nuclear reaction - Wikipedia

    en.wikipedia.org/wiki/Nuclear_reaction

    Expressed differently: the mass is reduced by 0.3%, corresponding to 0.3% of 90 PJ/kg is 270 TJ/kg. This is a large amount of energy for a nuclear reaction; the amount is so high because the binding energy per nucleon of the helium-4 nucleus is unusually high because the He-4 nucleus is " doubly magic ".

  7. Nuclear chain reaction - Wikipedia

    en.wikipedia.org/wiki/Nuclear_chain_reaction

    3) Both of those neutrons collide with uranium-235 atoms, each of which fissions and releases a few neutrons, which can then continue the reaction. In nuclear physics , a nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self ...

  8. Energy level splitting - Wikipedia

    en.wikipedia.org/wiki/Energy_level_splitting

    In quantum physics, energy level splitting or a split in an energy level of a quantum system occurs when a perturbation changes the system. The perturbation changes the corresponding Hamiltonian and the outcome is change in eigenvalues ; several distinct energy levels emerge in place of the former degenerate (multi- state ) level.

  9. Nuclear fission product - Wikipedia

    en.wikipedia.org/wiki/Nuclear_fission_product

    The sum of the atomic mass of the two atoms produced by the fission of one fissile atom is always less than the atomic mass of the original atom. This is because some of the mass is lost as free neutrons, and once kinetic energy of the fission products has been removed (i.e., the products have been cooled to extract the heat provided by the reaction), then the mass associated with this energy ...