1. Oxidation States and Redox: Oxidation and Reduction
CT04D01
Science 10
Chemistry

2. Halogens Alkali Metals Metaloids Non-metals Alkaline EarthsHe Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Alkaline Earths
Weak/Poor Metals
Transition Metals
Lanthanides
Noble Gases
Actinides

3. Ionic Charges All elements want to become like the noble gases!
Alkali Metals – lose 1 e
Alkaline Earths – Lose 2 e
IIIA – Lose 3 e
IVA (carbon) – Lose 4 e / Gain 4 e
VA (Nitrogen) – Gain 3 e
VIA (oxygen) – Gain 2 e
Halogen – Gain 1 e
Noble Gases - neutral
Ionic Charges H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Se Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

4. (BrINClHOF) Br2, O2, H2, Ne, Zn, Mg, Ca, etc
Oxidation Numbers
Oxidation numbers always refer to single atoms
The oxidation number of an uncombined element is always 0 (this includes diatomics)
(BrINClHOF) Br2, O2, H2, Ne, Zn, Mg, Ca, etc
The oxidation number of Hydrogen is usually +1
HCl, H2SO4
The oxidation number of Oxygen is usually -2
H2O, NO2, et
Oxidation numbers of monatomic ions follow the charge of the ion
O2-, Zn2+
The sum of oxidation numbers is zero for a neutral compound
LiMnO4
The sum of the oxdiation numbers is the charge of the polyatomic ion
SO42-, NO3-, PO33-
Only when in completely ionic binary compounds will Alkali Metals (+1), Alkaline Earths (+2), Halogens (-1)
NaCl, MgBr2, KF, etc

5. Polyatomic Ions
The polyatomic ions will be given to you but you should be very familiar with them by now!! Let’s determine oxidation numbers for each…. +1 -1 -2 -3
Ammonium NH4+
Chlorate
ClO3-
Sulfate
SO42-
Phosphate
PO43-
Chlorite
ClO2-
Sulfite
SO32-
Phosphite
Nitrate
NO3-
Carbonate CO32-
Nitrite
NO2-
Hydroxide
OH-

6. Practice Assigning Oxidation Numbers
NO2
N2O5
HClO3
HNO3
Ca(NO3)2
K2CO3

7. Practice Assigning Oxidation Numbers
NO2
N= +4, O = -2
N2O5
N = +5, O = -2
HClO3
H=+1, Cl=+5, O = -2
HNO3
H=+1, N = +5, O = -2
Ca(NO3)2
Ca=+2, N =+5, O= -2
K2CO3
K=+1, C=+4, O= -2
Hint: If it includes a polyatomic ion, you know the overall charge, and oxygen will always be -2, find the other oxidation states next

8. Practice Assigning Oxidation Numbers
Fe(OH)3
K3PO3
CO32-
(NH4)Cl
Fe(ClO2)2

9. Practice Assigning Oxidation Numbers
Fe(OH)3
Fe =+3, O=-2, H=+1
K3PO3
K=+1, P=+3, O=-2
CO32-
C=+4, O =-2
(NH4)Cl
N=3-, H=1+, Cl=-1
Fe(ClO2)2
Fe=+2, Cl=3+, O=-2

10. Redox Equations
NOTE: If you get there! Brakke students will need to identify which element is oxidized and which is reduced for a 7

11. Oxidation-Reduction Reactions
All redox reactions have at least one element oxidized and at least one element reduced
Occasionally the same element may undergo both oxidation and reduction.
This is known as an auto-oxidation reduction
We will NOT see this until IB CHEM

12. Pneumonic Devices….
There are two phrases to help you remember the general practice of oxidation and reduction exchanges
LEO says GER
OIL RIG

13. GER! LEO says….. LEO: Loss of Electrons = Oxidation
GER: Gain of Electrons = Reduction

14. OIL: Oxidation is Loss….
RIG: Reduction is Gain….
….of electrons

15. Oxidation Numbers
Oxidation is the loss of electrons; Reduction is the gain of electrons
Oxidation and reduction go together. Whenever a substance loses electrons another substance gains electrons
Oxidation Numbers are a system that we can use to keep track of electron transfers with a reaction

16. Using Oxidation Numbers
Careful examination of the oxidation numbers of atoms in an equation allows us to determine what is oxidized and what is reduced in an oxidation-reduction reaction

17. Using Oxidation Numbers
An increase in the oxidation number indicates that an atom has lost electrons and therefore oxidized.
A decrease in the oxidation number indicates that an atom has gained electrons and therefore reduced
Example
Zn CuSO4  ZnSO Cu
Zn:   Oxidized
Cu: +2   Reduced

18. Exercise
For each of the following reactions find the element oxidized and the element reduced
Cl KBr  KCl Br2
Cu HNO3  Cu(NO3) NO2 + H2O
HNO I  HIO NO2
Look on the following slides for answers……

19. Exercise 1
For each of the following reactions find the element oxidized and the element reduced
Cl KBr  KCl Br2
Br increases from –1 to 0  Oxidized
Cl decreases from 0 to –1  Reduced
K remains unchanged at +1

20. Exercise 2
For each of the following reactions find the element oxidized and the element reduced –
Cu HNO3  Cu(NO3) NO2 + H2O
Cu increases from 0 to +2  Oxidized
Some N in nitric acid from +5 to +4  Reduced
The nitrogen that ends up in copper nitrate remains unchanged, same for hydrogen and oxygen

21. Exercise 3
For each of the following reactions find the element oxidized and the element reduced
HNO I  HIO NO2
N is reduced from +5 to +4  Reduced
I is increased from 0 to +5  Oxidized
The hydrogen and oxygen remain unchanged.