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  2. Multiplicity (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Multiplicity_(chemistry)

    When S > L there are only 2L+1 orientations of total angular momentum possible, ranging from S+L to S-L. [2] [3] The ground state of the nitrogen atom is a 4 S state, for which 2S + 1 = 4 in a quartet state, S = 3/2 due to three unpaired electrons. For an S state, L = 0 so that J can only be 3/2 and there is only one level even though the ...

  3. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    Ubiquitousness and stability of atoms relies on their binding energy, which means that an atom has a lower energy than an unbound system of the nucleus and electrons. Where the temperature is much higher than ionization potential , the matter exists in the form of plasma —a gas of positively charged ions (possibly, bare nuclei) and electrons.

  4. Molecular orbital diagram - Wikipedia

    en.wikipedia.org/wiki/Molecular_orbital_diagram

    The orbital is not symmetric around the molecular axis and is therefore a pi orbital. The antibonding pi orbital (also asymmetrical) has four lobes pointing away from the nuclei. Both p y and p x orbitals form a pair of pi orbitals equal in energy and can have higher or lower energies than that of the sigma orbital.

  5. Molecular mechanics - Wikipedia

    en.wikipedia.org/wiki/Molecular_mechanics

    In molecular mechanics, several ways exist to define the environment surrounding a molecule or molecules of interest. A system can be simulated in vacuum (termed a gas-phase simulation) with no surrounding environment, but this is usually undesirable because it introduces artifacts in the molecular geometry, especially in charged molecules.

  6. Molecule - Wikipedia

    en.wikipedia.org/wiki/Molecule

    Also carbohydrates, for example, have the same ratio (carbon:hydrogen:oxygen= 1:2:1) (and thus the same empirical formula) but different total numbers of atoms in the molecule. The molecular formula reflects the exact number of atoms that compose the molecule and so characterizes different molecules. However different isomers can have the same ...

  7. Avogadro constant - Wikipedia

    en.wikipedia.org/wiki/Avogadro_constant

    The Avogadro constant, commonly denoted N A [1] or L, [2] is an SI defining constant with an exact value of 6.022 140 76 × 10 23 mol −1 (reciprocal moles). [3] [4] It defines the number of constituent particles in one mole, where the particles in question can be either molecules, atoms, ions, ion pairs, or any other elementary entities.

  8. Atomic orbital - Wikipedia

    en.wikipedia.org/wiki/Atomic_orbital

    Still, the Bohr model's use of quantized angular momenta and therefore quantized energy levels was a significant step toward the understanding of electrons in atoms, and also a significant step towards the development of quantum mechanics in suggesting that quantized restraints must account for all discontinuous energy levels and spectra in atoms.

  9. Electron configuration - Wikipedia

    en.wikipedia.org/wiki/Electron_configuration

    The molecular orbitals are labelled according to their symmetry, [e] rather than the atomic orbital labels used for atoms and monatomic ions; hence, the electron configuration of the dioxygen molecule, O 2, is written 1σ g 2 1σ u 2 2σ g 2 2σ u 2 3σ g 2 1π u 4 1π g 2, [39] [40] or equivalently 1σ g 2 1σ u 2 2σ g 2 2σ u 2 1π u 4 3σ g ...