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  2. Energy level - Wikipedia

    en.wikipedia.org/wiki/Energy_level

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

  3. Noble gas - Wikipedia

    en.wikipedia.org/wiki/Noble_gas

    The abundance of argon, on the other hand, is increased as a result of the beta decay of potassium-40, also found in the Earth's crust, to form argon-40, which is the most abundant isotope of argon on Earth despite being relatively rare in the Solar System. This process is the basis for the potassium-argon dating method. [72]

  4. Aufbau principle - Wikipedia

    en.wikipedia.org/wiki/Aufbau_principle

    For example, in copper 29 Cu, according to the Madelung rule, the 4s subshell (n + l = 4 + 0 = 4) is occupied before the 3d subshell (n + l = 3 + 2 = 5). The rule then predicts the electron configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 9 4s 2, abbreviated [Ar] 3d 9 4s 2 where [Ar] denotes the configuration of argon, the preceding noble gas.

  5. Oganesson - Wikipedia

    en.wikipedia.org/wiki/Oganesson

    Its second ionization energy should be around 1560 kJ/mol. [8] Even the shell structure in the nucleus and electron cloud of oganesson is strongly impacted by relativistic effects: the valence and core electron subshells in oganesson are expected to be "smeared out" in a homogeneous Fermi gas of electrons, unlike those of the "less relativistic ...

  6. 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.

  7. Argon - Wikipedia

    en.wikipedia.org/wiki/Argon

    Argon is the most abundant noble gas in Earth's crust, comprising 0.00015% of the crust. Nearly all argon in Earth's atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in Earth's crust. In the universe, argon-36 is by far the most common argon isotope, as it is the most easily produced by stellar nucleosynthesis in ...

  8. Carbon-based life - Wikipedia

    en.wikipedia.org/wiki/Carbon-based_life

    The most important characteristics of carbon as a basis for the chemistry of cellular life are that each carbon atom is capable of forming up to four valence bonds with other atoms simultaneously, and that the energy required to make or break a bond with a carbon atom is at an appropriate level for building large and complex molecules which may ...

  9. Electron configuration - Wikipedia

    en.wikipedia.org/wiki/Electron_configuration

    If that were the case, the 3d-orbital would have the same energy as the 3p-orbital, as it does in hydrogen, yet it clearly does not. There is no special reason why the Fe 2+ ion should have the same electron configuration as the chromium atom, given that iron has two more protons in its nucleus than chromium, and that the chemistry of the two ...