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The 18-electron rule is a rule used primarily for predicting formulae for stable metal complexes.<ref name="Check1" >{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref> The rule is based on the fact that the valence shells of transition metals consist of nine valence orbitals, which collectively can accommodate 18 electrons as either bonding or nonbonding electron pairs. This means that, the combination of these nine atomic orbitals with ligand orbitals creates nine molecular orbitals that are either metal-ligand bonding or non-bonding. When a metal complex has 18 valence electrons, it is said to have achieved the same electron configuration as the noble gas in the period. The rule and its exceptions are similar to the application of the octet rule to main group elements. The rule is not helpful for complexes of metals that are not transition metals, and interesting or useful transition metal complexes will violate the rule because of the consequences deviating from the rule bears on reactivity. The rule was first proposed by American chemist Irving Langmuir in 1921.<ref name="Check1" /><ref>The Origin of the 18-Electron Rule William B. Jensen Journal of Chemical Education 2005 82 (1), 28 doi:10.1021/ed082p28</ref>


18-Electron rule sections
Intro  Applicability of the 18-electron rule  Exceptions to the 18-electron rule  See also  References  Further reading  

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The 18-electron rule is a rule used primarily for predicting formulae for stable metal complexes.<ref name="Check1" >{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref> The rule is based on the fact that the valence shells of transition metals consist of nine valence orbitals, which collectively can accommodate 18 electrons as either bonding or nonbonding electron pairs. This means that, the combination of these nine atomic orbitals with ligand orbitals creates nine molecular orbitals that are either metal-ligand bonding or non-bonding. When a metal complex has 18 valence electrons, it is said to have achieved the same electron configuration as the noble gas in the period. The rule and its exceptions are similar to the application of the octet rule to main group elements. The rule is not helpful for complexes of metals that are not transition metals, and interesting or useful transition metal complexes will violate the rule because of the consequences deviating from the rule bears on reactivity. The rule was first proposed by American chemist Irving Langmuir in 1921.<ref name="Check1" /><ref>The Origin of the 18-Electron Rule William B. Jensen Journal of Chemical Education 2005 82 (1), 28 doi:10.1021/ed082p28</ref>


18-Electron rule sections
Intro  Applicability of the 18-electron rule  Exceptions to the 18-electron rule  See also  References  Further reading  

PREVIOUS: IntroNEXT: Applicability of the 18-electron rule
<<>>