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  2. Hund's rule of maximum multiplicity - Wikipedia

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

    For example, the nitrogen atom ground state has three unpaired electrons of parallel spin, so that the total spin is 3/2 and the multiplicity is 4. The lower energy and increased stability of the atom arise because the high-spin state has unpaired electrons of parallel spin, which must reside in different spatial orbitals according to the Pauli ...

  3. Aufbau principle - Wikipedia

    en.wikipedia.org/wiki/Aufbau_principle

    In this way, the electrons of an atom or ion form the most stable electron configuration possible. An example is the configuration 1s 2 2s 2 2p 6 3s 2 3p 3 for the phosphorus atom, meaning that the 1s subshell has 2 electrons, the 2s subshell has 2 electrons, the 2p subshell has 6 electrons, and so on.

  4. Multiplicity (chemistry) - Wikipedia

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

    Each has two electrons of opposite spin in the π* level so that S = 0 and the multiplicity is 2S + 1 = 1 in consequence. In the first excited state, the two π* electrons are paired in the same orbital, so that there are no unpaired electrons. In the second excited state, however, the two π* electrons occupy different orbitals with opposite spin.

  5. Pauli matrices - Wikipedia

    en.wikipedia.org/wiki/Pauli_matrices

    The Pauli matrices are some of the most important single-qubit operations. In that context, the Cartan decomposition given above is called the "Z–Y decomposition of a single-qubit gate". Choosing a different Cartan pair gives a similar "X–Y decomposition of a single-qubit gate.

  6. Molecular Hamiltonian - Wikipedia

    en.wikipedia.org/wiki/Molecular_Hamiltonian

    The elementary parts of a molecule are the nuclei, characterized by their atomic numbers, Z, and the electrons, which have negative elementary charge, −e. 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 ...

  7. Spin–statistics theorem - Wikipedia

    en.wikipedia.org/wiki/Spin–statistics_theorem

    The basic building blocks of matter such as protons, neutrons, and electrons are all fermions. Conversely, particles such as the photon, which mediate forces between matter particles, are all bosons. [citation needed] A spin–statistics theorem attempts to explain the origin of this fundamental dichotomy. [5]: 4

  8. Intersystem crossing - Wikipedia

    en.wikipedia.org/wiki/Intersystem_crossing

    That is, the spin of the excited electron is still paired with the ground state electron (a pair of electrons in the same energy level must have opposite spins, per the Pauli exclusion principle). In a triplet state the excited electron is no longer paired with the ground state electron; that is, they are parallel (same spin). Since excitation ...

  9. Tunnel magnetoresistance - Wikipedia

    en.wikipedia.org/wiki/Tunnel_magnetoresistance

    The spin-up electrons are those with spin orientation parallel to the external magnetic field, whereas the spin-down electrons have anti-parallel alignment with the external field. The relative resistance change is now given by the spin polarizations of the two ferromagnets, P 1 and P 2 :