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  2. History of atomic theory - Wikipedia

    en.wikipedia.org/wiki/History_of_atomic_theory

    After the neutron was discovered, scientists realized the helium nucleus in fact contained two protons and two neutrons. Discovery of the neutron Physicists in the 1920s believed that the atomic nucleus contained protons plus a number of "nuclear electrons" that reduced the overall charge.

  3. Timeline of atomic and subatomic physics - Wikipedia

    en.wikipedia.org/wiki/Timeline_of_atomic_and...

    The two discovering parties independently assign the discovered meson two different symbols, J and ψ; thus, it becomes formally known as the J/ψ meson. The discovery finally convinces the physics community of the quark model's validity. 1974 Robert J. Buenker and Sigrid D. Peyerimhoff introduce the multireference configuration interaction method.

  4. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    The number of protons in an atom (which Rutherford called the "atomic number" [27] [28]) was found to be equal to the element's ordinal number on the periodic table and therefore provided a simple and clear-cut way of distinguishing the elements from each other. The atomic weight of each element is higher than its proton number, so Rutherford ...

  5. Proton - Wikipedia

    en.wikipedia.org/wiki/Proton

    In chemistry, the number of protons in the nucleus of an atom is known as the atomic number, which determines the chemical element to which the atom belongs. For example, the atomic number of chlorine is 17; this means that each chlorine atom has 17 protons and that all atoms with 17 protons are chlorine atoms.

  6. Helium - Wikipedia

    en.wikipedia.org/wiki/Helium

    Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons. As in Newtonian mechanics, no system that consists of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem) and helium is no exception. Thus, numerical mathematical ...

  7. Atomic nucleus - Wikipedia

    en.wikipedia.org/wiki/Atomic_nucleus

    This depiction shows the particles as separate, whereas in an actual helium atom, the protons are superimposed in space and most likely found at the very center of the nucleus, and the same is true of the two neutrons. Thus, all four particles are most likely found in exactly the same space, at the central point.

  8. For All This Time, Protons Have Been Hiding Secret Mass ... - AOL

    www.aol.com/time-protons-hiding-secret-mass...

    Physicists have long known that protons are more massive than the stuff that makes them up, but we didn’t know where that mass was located. Now we do. For All This Time, Protons Have Been Hiding ...

  9. History of subatomic physics - Wikipedia

    en.wikipedia.org/wiki/History_of_subatomic_physics

    Many more types of subatomic particles have been found. Most such particles (but not electrons) were eventually found to be composed of even smaller particles such as quarks. Particle physics studies these smallest particles; nuclear physics studies atomic nuclei and their (immediate) constituents: protons and neutrons.