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. The rule is based on the fact that the valence orbitals of transition metals consist of five d orbitals, one s orbital and three p orbitals which can collectively 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 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.
Q2329
chemical
Concept
Q1398821
rule of thumb
Concept
Q19588
transition metal
Concept
Q237200
organometallic compounds
Concept
Q107414
valence orbital
Concept
Q53860
d orbitals
Concept
Q53860
s orbital
Concept
Q53860
p orbitals
Concept
Q2225
electron
Concept
Q53860
atomic orbitals
Concept
Q193161
ligand
Concept
Q725417
molecular orbital
Concept
Q19609
noble gas
Concept
Q184286
Irving Langmuir
PER
Q200104
18-electron rule
Concept
1921-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1921
DATE
+18^^http://www.w3.org/2001/XMLSchema#decimal
18
NUMBER
+18^^http://www.w3.org/2001/XMLSchema#decimal
18
NUMBER
+18^^http://www.w3.org/2001/XMLSchema#decimal
18
NUMBER
subclass of