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In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to other atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Conceptually, the oxidation state may be positive, negative or zero.
In some molecules, there is a difference between valence and oxidation state for a given atom. For example, in disulfur decafluoride molecule S 2 F 10, each sulfur atom has 6 valence bonds (5 single bonds with fluorine atoms and 1 single bond with the other sulfur atom). Thus, each sulfur atom is hexavalent or has valence 6, but has oxidation ...
Oxidation state is an important index to evaluate the charge distribution within molecules. [2] The most common definition of oxidation state was established by IUPAC, [3] which let the atom with higher electronegativity takes all the bonding electrons and calculated the difference between the number of electrons and protons around each atom to assign the oxidation states.
The oxidation state view of the CO 2 molecule is shown below: Oxidation states overemphasize the ionic nature of the bonding; the difference in electronegativity between carbon and oxygen is insufficient to regard the bonds as being ionic in nature. In reality, the distribution of electrons in the molecule lies somewhere between these two extremes.
"Oxide" itself is the dianion (anion bearing a net charge of –2) of oxygen, an O 2– ion with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating.
Some other mixed oxides with silver in non-integral oxidation states, namely Ag 2 O 3 and Ag 3 O 4, are also known, as is Ag 3 O which behaves as a metallic conductor. [ 44 ] Silver(I) sulfide , Ag 2 S, is very readily formed from its constituent elements and is the cause of the black tarnish on some old silver objects.
The stability has in part been correlated to differences in volatility between the lanthanide metals. [78] In EuB 6 and YbB 6 the metals have an oxidation state of +2 whereas in the rest of the lanthanide hexaborides it is +3. This rationalises the differences in conductivity, the extra electrons in the Ln III hexaborides entering conduction bands.
The naming of molybdates generally follows the convention of a prefix to show the number of Mo atoms present. For example, dimolybdate for 2 molybdenum atoms; trimolybdate for 3 molybdenum atoms, etc.. Sometimes the oxidation state is added as a suffix, such as in pentamolybdate(VI). The heptamolybdate ion, Mo 7 O 6− 24, is often called ...