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  2. Octet rule - Wikipedia

    en.wikipedia.org/wiki/Octet_rule

    For transition metals, molecules tend to obey the 18-electron rule which corresponds to the utilization of valence d, s and p orbitals to form bonding and non-bonding orbitals. However, unlike the octet rule for main-group elements, transition metals do not strictly obey the 18-electron rule and the valence electron count can vary between 12 ...

  3. Electron counting - Wikipedia

    en.wikipedia.org/wiki/Electron_counting

    Octet rule is used with Lewis structures for main group elements, especially the lighter ones such as carbon, nitrogen, and oxygen, 18-electron rule [2] in inorganic chemistry and organometallic chemistry of transition metals, Hückel's rule for the π-electrons of aromatic compounds,

  4. Multiplicity (chemistry) - Wikipedia

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

    Each is therefore an unpaired electron, but the total spin is zero and the multiplicity is 2S + 1 = 1 despite the two unpaired electrons. The multiplicity of the second excited state is therefore not equal to the number of its unpaired electrons plus one, and the rule which is usually true for ground states is invalid for this excited state.

  5. 18-electron rule - Wikipedia

    en.wikipedia.org/wiki/18-electron_rule

    The 18-electron rule is a chemical rule of thumb used primarily for predicting and rationalizing formulas for stable transition metal complexes, especially organometallic compounds. [1] The rule is based on the fact that the valence orbitals in the electron configuration of transition metals consist of five ( n −1)d orbitals, one n s orbital ...

  6. d electron count - Wikipedia

    en.wikipedia.org/wiki/D_electron_count

    When a transition metal atom loses one or more electrons to form a positive ion, overall electron repulsion is reduced and the n d orbital energy is lowered more than the (n+1) s orbital energy. The ion is formed by removal of the outer s electrons and tends to have a d n configuration, [ 3 ] : 40 even though the s subshell is added to neutral ...

  7. Polyhedral skeletal electron pair theory - Wikipedia

    en.wikipedia.org/wiki/Polyhedral_skeletal...

    For each transition metal present, 10 electrons are subtracted from the total electron count. For example, in Rh 6 (CO) 16 the total number of electrons would be 6 × 9 + 16 × 2 − 6 × 10 = 86 – 60 = 26. Therefore, the cluster is a closo polyhedron because n = 6, with 4n + 2 = 26. S 2+ 4

  8. Hund's rules - Wikipedia

    en.wikipedia.org/wiki/Hund's_rules

    Hund's first rule states that the lowest energy atomic state is the one that maximizes the total spin quantum number for the electrons in the open subshell. The orbitals of the subshell are each occupied singly with electrons of parallel spin before double occupation occurs.

  9. Jemmis mno rules - Wikipedia

    en.wikipedia.org/wiki/Jemmis_mno_rules

    In chemistry, the Jemmis mno rules represent a unified rule for predicting and systematizing structures of compounds, usually clusters.The rules involve electron counting. They were formulated by E. D. Jemmis to explain the structures of condensed polyhedral boranes such as B 20 H 16, which are obtained by condensing polyhedral boranes by sharing a triangular face, an edge, a single vertex, or ...