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Oxidation number

 

 
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Oxidation number
 
 
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The oxidation number of a central atom in a coordination compound
Complex (chemistry)

In chemistry, a complex, also called a "coordination compound" or "metal complex", is a structure consisting of a central atom or molecule connected to surrounding atoms or molecules....
 is the charge that it would have if all the ligand
Ligand

In chemistry, a ligand is either an atom, ion, or molecule that bonds to a central metal, generally involving formal donation of one or more of its electrons....
s were removed along with the electron pair
Electron pair

In chemistry, an electron pair consists of two electrons that occupy the same molecular orbital but have opposite spin_s.Because electrons are fermions, the Pauli exclusion principle forbids these particles from having exactly the same quantum numbers....
s that were shared with the central atom. It is used in the nomenclature of inorganic compounds. It is represented by a Roman numeral; the plus sign is omitted for positive oxidation numbers. The oxidation number is placed either as a right superscript to the element symbol, e.g.






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The oxidation number of a central atom in a coordination compound
Complex (chemistry)

In chemistry, a complex, also called a "coordination compound" or "metal complex", is a structure consisting of a central atom or molecule connected to surrounding atoms or molecules....
 is the charge that it would have if all the ligand
Ligand

In chemistry, a ligand is either an atom, ion, or molecule that bonds to a central metal, generally involving formal donation of one or more of its electrons....
s were removed along with the electron pair
Electron pair

In chemistry, an electron pair consists of two electrons that occupy the same molecular orbital but have opposite spin_s.Because electrons are fermions, the Pauli exclusion principle forbids these particles from having exactly the same quantum numbers....
s that were shared with the central atom. It is used in the nomenclature of inorganic compounds. It is represented by a Roman numeral; the plus sign is omitted for positive oxidation numbers. The oxidation number is placed either as a right superscript to the element symbol, e.g. FeIII, or in parentheses after the name of the element, e.g. iron(III): in the latter case, there is no space between the element name and the oxidation number.

The oxidation number is usually numerically equal to the oxidation state
Oxidation state

In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical Electrical charge that an atom would have if all bonds to atoms of different elements were 100% Ionic bond....
. However, in a few cases the ligand atom can be less electronegative than the central atom (e.g., in iridium phosphine complexes), resulting in a formal oxidation state that is different from the oxidation number.

Spectroscopic oxidation states


Although formal oxidation numbers can be helpful for classifying compounds, they are unmeasureable and their physical meaning can be ambiguous. Formal oxidation numbers require particular caution for molecules where the bonding is covalent, since the formal oxidation numbers require the heterolytic removal of ligand
Ligand

In chemistry, a ligand is either an atom, ion, or molecule that bonds to a central metal, generally involving formal donation of one or more of its electrons....
s, which essentially denies covalency. Spectroscopic oxidation states, as defined by Jorgenson and reiterated by Wieghardt, are measureables that are bench-marked using spectroscopic and crystallographic data.

See also

  • List of oxidation states of the elements
    List of oxidation states of the elements

    This is a list of all the known oxidation states of the chemical elements, excluding nonintegral values. The more common oxidation states are highlighted....