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  2. Bohr model - Wikipedia

    en.wikipedia.org/wiki/Bohr_model

    The Bohr model is a relatively primitive model of the hydrogen atom, compared to the valence shell model. As a theory, it can be derived as a first-order approximation of the hydrogen atom using the broader and much more accurate quantum mechanics and thus may be considered to be an obsolete scientific theory.

  3. Helium - Wikipedia

    en.wikipedia.org/wiki/Helium

    hexagonal close-packed (hcp) Category: Helium. Helium (from Greek: ἥλιος, romanized: helios, lit. 'sun') is a chemical element; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table.

  4. Helium atom - Wikipedia

    en.wikipedia.org/wiki/Helium_atom

    Helium is composed of two electrons bound by the electromagnetic force to a nucleus containing two protons along with two neutrons, depending on the isotope, held together by the strong force. Unlike for hydrogen, a closed-form solution to the Schrödinger equation for the helium atom has not been found.

  5. Atomic orbital - Wikipedia

    en.wikipedia.org/wiki/Atomic_orbital

    To see the elongated shape of ψ (x, y, z)2 functions that show probability density more directly, see pictures of d-orbitals below. In quantum mechanics, an atomic orbital (/ ˈɔːrbɪtəl /) is a function describing the location and wave-like behavior of an electron in an atom. [1] This function describes an electron's charge distribution ...

  6. Bohr–Sommerfeld model - Wikipedia

    en.wikipedia.org/wiki/Bohr–Sommerfeld_model

    The Bohr–Sommerfeld model (also known as the Sommerfeld model or Bohr–Sommerfeld theory) was an extension of the Bohr model to allow elliptical orbits of electrons around an atomic nucleus. Bohr–Sommerfeld theory is named after Danish physicist Niels Bohr and German physicist Arnold Sommerfeld. Sommerfeld argued that if electronic orbits ...

  7. Bohr radius - Wikipedia

    en.wikipedia.org/wiki/Bohr_radius

    The Bohr radius (⁠ ⁠) is a physical constant, approximately equal to the most probable distance between the nucleus and the electron in a hydrogen atom in its ground state. It is named after Niels Bohr, due to its role in the Bohr model of an atom. Its value is 5.291 772 105 44(82) × 10−11 m. [1][2]

  8. History of atomic theory - Wikipedia

    en.wikipedia.org/wiki/History_of_atomic_theory

    History of atomic theory. The current theoretical model of the atom involves a dense nucleus surrounded by a probabilistic "cloud" of electrons. Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years in response to scientific discoveries.

  9. Electron configuration - Wikipedia

    en.wikipedia.org/wiki/Electron_configuration

    In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. [ 1 ] For example, the electron configuration of the neon atom is 1s2 2s2 2p6, meaning that the 1s, 2s, and 2p subshells are occupied by two, two, and six ...