Redox reactions- reactions in which one or more electrons is transferred
Oxidation and Reduction When a metal undergoes corrosion it
loses electrons to form cations:
Ca(s) +2H+(aq) Ca2+(aq) + H2(g) Oxidized: atom, molecule, or ion
becomes more positively charged. Oxidation is the loss of electrons.
Reduced: atom, molecule, or ion becomes less positively charged. Reduction is the gain of electrons.
Vanadium compounds having different oxidation numbers or oxidation states
How do maximum and minimum values of the oxidation number correlate with the position in the periodic table?
The oxidation number of an atom in an element is 0.Ex: Na (s), O2 (g), Hg (l)
The oxidation state of a monatomic ion is the same as its chargeEx. Na + = +1 Cl - = -1
Fluorine has an oxidation number of -1 in its compounds
Oxygen usually has an oxidation number of -2 in its compounds. There are some exceptions:
a. Oxygen has an oxidation number of -1 in peroxides, which contain the O2
2- ion.b. Oxygen has an oxidation number of -
1/2 in superoxides, which contain the O2
- ion.
Hydrogen has an oxidation number of +1 unless it is combined with metals, in which case it has an oxidation number of -1.
The sum of the oxidation numbers of all atoms in a substance must equal the total charge on the species: 0 for molecules; the ionic charge for ions.
The position of the element in the periodic table may be useful:a. Group IA (1) elements have oxidation numbers
of +1 in their compounds.b. Group IIA (2) elements have oxidation numbers
of +2 in their compounds.c. Group VIIA (17) elements have oxidation
numbers of -1 unless combined with oxygen or a halogen closer to the top of the group.
d. In binary compounds, Group VIA (16) elements have oxidation numbers of -2, unless
combined with oxygen or halogens.
General Summary
Element: 0Fluorine: -1Oxygen: -2Hydrogen: +1
H2SO4
H is +1 S is -2 unless combined with oxygen or a
halogen, so leave this for last O is -2 Use summation rule for S:
2(+1) + 1(S) + 4(-2) = 0 S = 0 - 2 + 8 = +6
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2
CCl4 H2O2
NO3- MnO4
-
CO2 NaNO3
KClO4
Determine values of the oxidation number of each element in these compounds or ions:
H2O O(-2) H(+1) SO2
CCl4 H2O2
NO3- MnO4
-
CO2 NaNO3
KClO4
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2
CCl4 Cl (-1) C (+4) H2O2
NO3- MnO4
-
CO2 NaNO3
KClO4
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2
CCl4 H2O2
NO3- O(-2) N(+5) MnO4
-
CO2 NaNO3
KClO4
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2
CCl4 H2O2
NO3- MnO4
-
CO2 O(-2) C(+4) NaNO3
KClO4
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2
CCl4 H2O2
NO3- MnO4
-
CO2 NaNO3
KClO4 O (-2) K (+1) Cl (+7)
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2 O(-2) S(+4)
CCl4 H2O2
NO3- MnO4
-
CO2 NaNO3
KClO4
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2
CCl4 H2O2 H(+1) O(-1)
NO3- MnO4
-
CO2 NaNO3
KClO4
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2
CCl4 H2O2
NO3- MnO4
- O(-2) Mn(+7)
CO2 NaNO3
KClO4
Determine values of the oxidation number of each element in these compounds or ions:
H2O SO2
CCl4 H2O2
NO3- MnO4
-
CO2 NaNO3 O(-2) Na(+1) N(+5)
KClO4
Oxidation- increase in oxidation state Loss of electrons
Reduction- decrease in oxidation state Gain of electrons
LEO goes GER
2Na(s) + Cl2(g) 2NaCl(s)
What substances are being oxidized and reduced?