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  2. Hückel method - Wikipedia

    en.wikipedia.org/wiki/Hückel_method

    The theory predicts two energy levels for ethylene with its two π electrons filling the low-energy HOMO and the high energy LUMO remaining empty. In butadiene the 4 π-electrons occupy 2 low energy molecular orbitals, out of a total of 4, and for benzene 6 energy levels are predicted, two of them degenerate .

  3. Hund's rule of maximum multiplicity - Wikipedia

    en.wikipedia.org/wiki/Hund's_Rule_of_Maximum...

    A high multiplicity state is therefore the same as a high-spin state. The lowest-energy state with maximum multiplicity usually has unpaired electrons all with parallel spin. Since the spin of each electron is 1/2, the total spin is one-half the number of unpaired electrons, and the multiplicity is the number of unpaired electrons + 1.

  4. Binding energy - Wikipedia

    en.wikipedia.org/wiki/Binding_energy

    The atomic binding energy derives from the electromagnetic interaction of the electrons with the nucleus, mediated by photons. For an atom of helium, with 2 electrons, the atomic binding energy is the sum of the energy of first ionization (24.587 eV) and the energy of second ionization (54.418 eV), for a total of 79.005 eV. Atomic level

  5. Separation energy - Wikipedia

    en.wikipedia.org/wiki/Separation_energy

    If the energy of the incident photon exceeds the separation energy, a photodisintegration might occur. Energy in excess of the threshold value becomes kinetic energy of the ejected particle. By contrast, nuclear binding energy is the energy needed to completely disassemble a nucleus, or the energy released when a nucleus is assembled from ...

  6. Molecular Hamiltonian - Wikipedia

    en.wikipedia.org/wiki/Molecular_Hamiltonian

    Their interaction gives a nuclear charge of Z + q, where q = −eN, with N equal to the number of electrons. Electrons and nuclei are, to a very good approximation, point charges and point masses. The molecular Hamiltonian is a sum of several terms: its major terms are the kinetic energies of the electrons and the Coulomb (electrostatic ...

  7. Hückel's rule - Wikipedia

    en.wikipedia.org/wiki/Hückel's_rule

    8 (cyclooctatetraenide anion), with ten π electrons obeys the 4n + 2 rule for n = 2 and is planar, while the 1,4-dimethyl derivative of the dication, with six π electrons, is also believed to be planar and aromatic. [8] The Cyclononatetraenide anion (C 9 H – 9) is the largest all-cis monocyclic annulene/annulenyl system that is planar and ...

  8. Band gap - Wikipedia

    en.wikipedia.org/wiki/Band_gap

    The Pauli exclusion principle limits the number of electrons in a single orbital to two, and the bands are filled beginning with the lowest energy. In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist.

  9. Energy level - Wikipedia

    en.wikipedia.org/wiki/Energy_level

    This equation is obtained from combining the Rydberg formula for any hydrogen-like element (shown below) with E = hν = hc / λ assuming that the principal quantum number n above = n 1 in the Rydberg formula and n 2 = ∞ (principal quantum number of the energy level the electron descends from, when emitting a photon).