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  2. Proton - Wikipedia

    en.wikipedia.org/wiki/Proton

    A proton is a stable subatomic particle, symbol. p. , H +, or 1 H + with a positive electric charge of +1 e (elementary charge). Its mass is slightly less than the mass of a neutron and approximately 1836 times the mass of an electron (the proton-to-electron mass ratio). Protons and neutrons, each with a mass of approximately one atomic mass ...

  3. Quark - Wikipedia

    en.wikipedia.org/wiki/Quark

    1 / 3 ⁠. A quark (/ kwɔːrk, kwɑːrk /) is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. [1] All commonly observable matter is composed of up quarks, down quarks and electrons.

  4. Atomic nucleus - Wikipedia

    en.wikipedia.org/wiki/Atomic_nucleus

    The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment. After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko [1 ...

  5. List of physical constants - Wikipedia

    en.wikipedia.org/wiki/List_of_physical_constants

    The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured.

  6. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    Electrons and a compact nucleus of protons and neutrons. Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other by the number of protons that are in their atoms.

  7. Atomic number - Wikipedia

    en.wikipedia.org/wiki/Atomic_number

    Atomic number is the number of protons, and therefore also the total positive charge, in the atomic nucleus. The Rutherford–Bohr model of the hydrogen atom (Z = 1) or a hydrogen-like ion (Z > 1). In this model, it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron ...

  8. Annihilation - Wikipedia

    en.wikipedia.org/wiki/Annihilation

    t. e. In particle physics, annihilation is the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles, such as an electron colliding with a positron to produce two photons. [1] The total energy and momentum of the initial pair are conserved in the process and distributed among a set of ...

  9. Nuclear structure - Wikipedia

    en.wikipedia.org/wiki/Nuclear_structure

    The liquid drop model is one of the first models of nuclear structure, proposed by Carl Friedrich von Weizsäcker in 1935. [5] It describes the nucleus as a semiclassical fluid made up of neutrons and protons, with an internal repulsive electrostatic force proportional to the number of protons. The quantum mechanical nature of these particles ...