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?