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  2. Spin quantum number - Wikipedia

    en.wikipedia.org/wiki/Spin_quantum_number

    Spin quantum numbers apply also to systems of coupled spins, such as atoms that may contain more than one electron. Capitalized symbols are used: S for the total electronic spin, and m S or M S for the z-axis component. A pair of electrons in a spin singlet state has S = 0, and a pair in the triplet state has S = 1, with m S = −1, 0, or +1.

  3. Arrow pushing - Wikipedia

    en.wikipedia.org/wiki/Arrow_pushing

    The designations 1,2 and 1,4 are derived from numbering the atoms of the starting compound where the oxygen is labeled “1” and each atom adjacent to the oxygen are sequentially numbered out to the site of nucleophilic addition. A 1,2-addition occurs with nucleophilic addition to position 2 while a 1,4-addition occurs with nucleophilic ...

  4. VSEPR theory - Wikipedia

    en.wikipedia.org/wiki/VSEPR_theory

    The ammonia molecule (NH 3) has three pairs of electrons involved in bonding, but there is a lone pair of electrons on the nitrogen atom. [1]: 392–393 It is not bonded with another atom; however, it influences the overall shape through repulsions. As in methane above, there are four regions of electron density.

  5. Singlet state - Wikipedia

    en.wikipedia.org/wiki/Singlet_state

    The ability of positronium to form both singlet and triplet states is described mathematically by saying that the product of two doublet representations (meaning the electron and positron, which are both spin-1/2 doublets) can be decomposed into the sum of an adjoint representation (the triplet or spin 1 state) and a trivial representation (the ...

  6. 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 ...

  7. Triplet state - Wikipedia

    en.wikipedia.org/wiki/Triplet_state

    It is particularly important for systems at atomic length scales, such as individual atoms, protons, or electrons. A triplet state occurs in cases where the spins of two unpaired electrons, each having spin s = 1/2, align to give S = 1, in contrast to the more common case of two electrons aligning oppositely to give S = 0, a spin singlet.

  8. Electron counting - Wikipedia

    en.wikipedia.org/wiki/Electron_counting

    ionic counting: C 4− contributes 8 electrons, each proton contributes 0 each: 8 + 4 × 0 = 8 electrons. Similar for H: neutral counting: H contributes 1 electron, the C contributes 1 electron (the other 3 electrons of C are for the other 3 hydrogens in the molecule): 1 + 1 × 1 = 2 valence electrons. ionic counting: H contributes 0 electrons ...

  9. Unpaired electron - Wikipedia

    en.wikipedia.org/wiki/Unpaired_electron

    [1] Relatively more stable entities with unpaired electrons do exist, e.g. the nitric oxide molecule has one. According to Hund's rule, the spins of unpaired electrons are aligned parallel and this gives these molecules paramagnetic properties. The most stable examples of unpaired electrons are found on the atoms and ions of lanthanides and ...