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  2. Atomic orbital - Wikipedia

    en.wikipedia.org/wiki/Atomic_orbital

    For example, the orbital 1s (pronounced as the individual numbers and letters: "'one' 'ess'") is the lowest energy level (n = 1) and has an angular quantum number of ℓ = 0, denoted as s. Orbitals with ℓ = 1, 2 and 3 are denoted as p, d and f respectively. The set of orbitals for a given n and ℓ is called a subshell, denoted

  3. Hückel method - Wikipedia

    en.wikipedia.org/wiki/Hückel_method

    The variational theorem guarantees that the lowest value of that gives rise to a nontrivial (that is, not all zero) solution vector (,, …,) represents the best LCAO approximation of the energy of the most stable π orbital; higher values of with nontrivial solution vectors represent reasonable estimates of the energies of the remaining π ...

  4. Molecular orbital - Wikipedia

    en.wikipedia.org/wiki/Molecular_orbital

    The orbital wave functions are positive in the red regions and negative in the blue. The right column shows virtual MO's which are empty in the ground state, but may be occupied in excited states. In chemistry, a molecular orbital (/ ɒr b ə d l /) is a mathematical function describing the location and wave-like behavior of an electron in a ...

  5. Hartree–Fock method - Wikipedia

    en.wikipedia.org/wiki/Hartree–Fock_method

    The solution and are called molecular orbital and orbital energy respectively. Although Hartree-Fock equation appears in the form of a eigenvalue problem, the Fock operator itself depends on ϕ {\displaystyle \phi } and must be solved by a different technique.

  6. Slater-type orbital - Wikipedia

    en.wikipedia.org/wiki/Slater-type_orbital

    Some quantum chemistry software uses sets of Slater-type functions (STF) analogous to Slater type orbitals, but with variable exponents chosen to minimize the total molecular energy (rather than by Slater's rules as above). The fact that products of two STOs on distinct atoms are more difficult to express than those of Gaussian functions (which ...

  7. List of unsolved problems in chemistry - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    This is a list of unsolved problems in chemistry. Problems in chemistry are considered unsolved when an expert in the field considers it unsolved or when several experts in the field disagree about a solution to a problem.

  8. Molecular orbital diagram - Wikipedia

    en.wikipedia.org/wiki/Molecular_orbital_diagram

    The possible orbital symmetries are listed in the table below. For example, an orbital of B 1 symmetry (called a b 1 orbital with a small b since it is a one-electron function) is multiplied by -1 under the symmetry operations C 2 (rotation about the 2-fold rotation axis) and σ v '(yz) (reflection in the molecular

  9. Localized molecular orbitals - Wikipedia

    en.wikipedia.org/wiki/Localized_molecular_orbitals

    The localized orbital corresponding to one O-H bond is the sum of these two delocalized orbitals, and the localized orbital for the other O-H bond is their difference; as per Valence bond theory. For multiple bonds and lone pairs, different localization procedures give different orbitals .