5.2 Oxidation Numbers What we need to learn… determine the following: –the oxidation number of an atom in a chemical species –the change in oxidation number an atom undergoes when it is oxidized or reduced –whether an atom has been oxidized or reduced by its change in oxidation number relate change in oxidation number to gain or loss of electrons

Oxidation Numbers HV 2 O 4 -  V 6+ Is the above equation oxidation or reduction? Oxidation numbers are used to quickly determine if oxidation or reduction has occurred in a redox reaction. OXIDATION NUMBER: The charge that an atom would possess if the species containing the atom were made up of ions. Oxidation numbers are a somewhat fictitious concept, but, by using them, we can create half-reactions and use them in situations where no such half- reactions actually exist The use of both half-reactions and oxidation numbers are simply procedures which can be used to get us to a balanced REDOX equation; whether the half- reactions or oxidation numbers are real is irrelevant.

Rules for Oxidation NumbersOxidation # 1.All elements are zero:

Rules for Oxidation NumbersOxidation # 1.All elements are zero: N 2

Rules for Oxidation NumbersOxidation # 1.All elements are zero: N 2 0

Rules for Oxidation NumbersOxidation # 1.All elements are zero: N 2 0 Pb

Rules for Oxidation NumbersOxidation # 1.All elements are zero: N 2 0 Pb 0

Rules for Oxidation NumbersOxidation # 1.All elements are zero: N 2 0 Pb 0 Na

Rules for Oxidation NumbersOxidation # 1.All elements are zero: N 2 0 Pb 0 Na0

Rules for Oxidation NumbersOxidation # 1.All elements are zero: N 2 0 Pb 0 Na0 O 2

Rules for Oxidation NumbersOxidation # 1.All elements are zero: N 2 0 Pb 0 Na0 O 2 0

Rules for Oxidation NumbersOxidation # 2.Ions are their charge Na +

Rules for Oxidation NumbersOxidation # 2.Ions are their charge Na + +1

Rules for Oxidation NumbersOxidation # 2.Ions are their charge Na + +1 Br -

Rules for Oxidation NumbersOxidation # 2.Ions are their charge Na + +1 Br - -1

Rules for Oxidation NumbersOxidation # 2.Ions are their charge Na + +1 Br - -1 MgSO 4

Rules for Oxidation NumbersOxidation # 2.Ions are their charge Na + +1 Br - -1 MgSO 4 +2

Rules for Oxidation NumbersOxidation # 2.Ions are their charge Na + +1 Br - -1 MgSO 4 +2 Al 2 O 3

Rules for Oxidation NumbersOxidation # 2.Ions are their charge Na + +1 Br - -1 MgSO 4 +2 Al 2 O 3 -2

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2. Na 2 O

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2. Na 2 O-2

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2. Na 2 O-2 CO 2

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2. Na 2 O-2 CO 2 -2

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2. Na 2 O-2 CO 2 -2 O 2

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2. Na 2 O-2 CO 2 -2 O 2 0

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2. Na 2 O-2 CO 2 -2 O 2 0 CH 3 COOH

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2. Na 2 O-2 CO 2 -2 O 2 0 CH 3 COOH-2

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2 or in peroxides -1. Na 2 O-2 CO 2 -2 O 2 0 CH 3 COOH-2 HOOH

Rules for Oxidation NumbersOxidation # 3.The oxidation number of O in a compound is –2 or in peroxides -1. Na 2 O-2 CO 2 -2 O 2 0 CH 3 COOH-2 HOOH exception-1

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1.

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1. H 2 O

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1. H 2 O+1

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1 H 2 O+1 C 12 H 24 O 11

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1 H 2 O+1 C 12 H 24 O 11 +1

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1 H 2 O+1 C 12 H 24 O H 2

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1 H 2 O+1 C 12 H 22 O H 2 0

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1 or in metal hydrides -1. H 2 O+1 C 12 H 24 O H 2 0 NaH

Rules for Oxidation NumbersOxidation # 4.The oxidation number for H in a compound is +1 or in metal hydrides -1. H 2 O+1 C 12 H 24 O H 2 0 NaH-1

Rules for Oxidation NumbersOxidation # 5. All alkali and Alkali Earth metals within a chemical species will be their traditional combining capacity (group 1 [= +1] and 2 [+2] on PT) 6. Most often the halogens (group 17) will be their traditional charge within a chemical species (-1) NaCl (+1 and -1 respectively) HClO 3 (+1, +5* and -2 respectively) *not always -1

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # SO 4 2-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s SO 4 2-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 SO 4 2-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 SO 4 2- Total charge

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 SO 4 2- Total charge -8

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 SO 4 2- Total charge -8 = -2

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 SO 4 2- Total charge+6 -8 = -2

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s+6 -2 SO 4 2- Total charge+6 -8 = -2

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s SO 4 2- Total charge+6 -8 = -2

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # PO 4 3-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s PO 4 3-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 PO 4 3-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 PO 4 3- Total charge

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 PO 4 3- Total charge -8

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 PO 4 3- Total charge -8 = -3

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 PO 4 3- Total charge+5 -8 = -3

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s+5 -2 PO 4 3- Total charge+5 -8 = -3

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s PO 4 3- Total charge+5 -8 = -3

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # Cr 2 O 7 2-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s Cr 2 O 7 2-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 Cr 2 O 7 2-

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 Cr 2 O 7 2- Total charge

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 Cr 2 O 7 2- Total charge -14

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 Cr 2 O 7 2- Total charge -14 = -2

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 Cr 2 O 7 2- Total charge = -2

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s -2 Divide by 2 Cr 2 O 7 2- Total charge = -2

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s Cr 2 O 7 2- Total charge = -2

Rules for Oxidation Numbers 5.All other oxidation numbers are assigned so that the sum of all of the oxidation numbers is equal to the charge on the chemical species. Oxidation # oxidation #s Cr 2 O 7 2- Total charge = -2

Oxidation # Ca(NO 3 ) 2

Oxidation # +2 Ca(NO 3 ) 2

Oxidation # +2 Ca(NO 3 ) 2 +2

Oxidation # Na 2 C 2 O 4

Oxidation # Na 2 C 2 O = 0

Oxidation # Na 2 C 2 O = 0

Oxidation # Na 2 C 2 O = 0

Oxidation # CH 3 COOH

Oxidation # Rewrite C 2 H 4 O 2

Oxidation # Rewrite C 2 H 4 O = 0

Oxidation # Zn(OH) 4 2-

Oxidation # Zn(OH) = -2

Oxidation # H 2 PtCl 6

Oxidation # H 2 PtCl = 0

Oxidation # Na 2 O 2

Oxidation # Na 2 O = 0 Exception - does not work, O must be -1

Oxidation # Na 2 O = 0 Exception - does not work, O must be -1

Oxidation # CaH 2

Oxidation # CaH = 0 Exception - does not work, H must be -1

Oxidation # CaH = 0 Exception - does not work, H must be -1

Oxidation Numbers Using oxidation numbers in REDOX equations: HV 2 O 4 -  V 6+ Is the above equation oxidation or reduction?

Oxidation Numbers HV 2 O 4 -  V 6+ Is the above equation oxidation or reduction?

Oxidation Numbers Increase HV 2 O 4 -  V 6+ Is the above equation oxidation or reduction? If the oxidation number increases it is oxidation.

Homework…. Read SWB pages Do exercises #3-5 page 194 and # 6 page 195