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Oxidation Numbers

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Updated 2009-03-26 23:29

Oxidation States

Useful in oxidation-reduction (redox) reactions.

 

RuleAnswer
An atom in an element has this oxidation state0
A monatomic ion with charge +n has this oxidation state+n
A monatomic ion with charge -n has this oxidation state-n
Most O in covalent compounds have this oxidation state-2
O in peroxides have this oxidation state-1
H in covalent compounds with nonmetals have this oxidation state+1
Flourine always has this charge and oxidation state*-1
In binary compounds, the element that more strongly attracts electrons gets a negative charge -n and this oxidation state-n
The sum of oxidation states for all atoms in a neutral compound0
The sum of oxidation states for all atoms in a compound with charge +n+n
The sum of oxidation states for all atoms in a compound with charge -n-n
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* This rule above does not seem to apply in HOF where F has the oxidation state +1,
   as listed below.

 

Fill in the blankAnswer
Atoms with oxidation states that rise during a reaction are ___.oxidized
Atoms with oxidation states that fall during a reaction are ___.reduced
Atoms that gain electrons during a reaction are ____.reduced
Atoms that lose electrons during a reaction are ____.oxidized
An oxidizing agent contains an atom that is ____ during a reaction.reduced
A reducing agent contains an atom that is ____ during a reaction.oxidized
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AtomOxidation State
Na(s)0
Al(s)0
Hg(l)0
O in O20
O in O30
I in I20
Cl in Cl20
Na++1
Fe3++3
Mn2++2
H--1
H in H2--1/2
H in LiH-1
Li in LiH+1
H in CaH2-1
Ca in CaH2+2
O in H2O2-1
H in H2O2+1
O in O22--1
O in O2--1/2
K in KO2+1
O in KO2-1/2
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AtomOxidation State
S in S2O32-+2
O in S2O32--2
S in S4O62-+5/2
O in S4O62--2
Fe in Fe3O4+8/3 (actually two are +3 and one is +2)
O in Fe3O4-2
C in CH4-4
H in CH4+1
C in CO2+4
O in CO2-2
H in H2O+1
O in H2O-2
Na in NaCl+1
Cl in NaCl-1
S in PbS-2
Pb in PbS+2
S in SO2+4
O in SO2-2
Cr in Cr2O72-+6
O in Cr2O72--2
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AtomOxidation State
N in NH3-3
N in N2H4-2
N in NH2OH-1
N in N20
N in N2O+1
N in NO+2
N in N2O3+3
N in NO2+4
N in HNO3+5
S in SO3+6
S in H2SO4+6
S in SO42-+6
S in SF6+6
S in SO2 +4
S in HSO3-+4
S in SO32-+4
S in SF4+4
S in SCl2+2
S in S80
S in H2S-2
S in S2--2
Halogen in HOF, HOCl, HOBr, HOI+1
Halogen in HOClO+3
Halogen in HOClO2, HOBrO2, HOIO2+5
Halogen in HOClO3, HOBrO3, HOIO3+7
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Reference

Chemistry by Steven S. Zumdahl, D.C. Heath and Company, 1986.

 

Oxidation Numbers 2 and Oxidation Numbers 3 give more.

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