This presentation is designed for teaching the concepts oxidation reduction to students using the 5E strategy.

1. Oxidation
Reduction
Jinan Karameh Shayya

2. Engage
What does the word oxidation mean?
a. reaction with oxygen
b. losing electron during reaction
c. gaining electron during reaction

3. Explore
1. Name the materials used
in the first diagram
2. Describe what you see
in the second diagram?
3. Mg is oxidized. From this
reaction explain the meaning
of oxidation.

4. Explain
What does the word oxidation mean?
In ancient times, the word oxidation is related
to the reaction with oxygen. When an atom
reacts with oxygen it tends to lose electrons
and it is said to be oxidized. Now, all atoms
that lose electrons in a chemical reaction are
said to be oxidized or making oxidation.

5. Oxidation Number
It indicates if electrons are lost or gained by
an atom during a chemical reaction.
2Mg0 + O0
2 2 [ Mg+2 O-2]
Mg lost 2 electrons while Oxygen gained 2
electrons. The number above each atom/ion
is its oxidation number.

6. Oxidation number Rules
Rule 1: In its pure elemental form, an atom
has an oxidation number of zero

7. Oxidation number Rules
Rule 2: The oxidation number of an ion is the
same as its charge

8. Oxidation number Rules
Rule 3: The oxidation number of metals is +1
in group 1 and +2 in group 2

9. Oxidation number Rules
Rule 4: Hydrogen has two possible oxidation
numbers: +1 (if bonded with nonmetals) and
-1 (if bonded with metals)

10. Oxidation number Rules
Rule 5: Combined Al has oxidation number
+3, and combined F and Cl have oxidation
number -1 each.
Rule 6: Oxygen has oxidation number -2
except in peroxides it will be -1.

11. Oxidation number Rules
Rule 7: The algebraic sum of oxidation
numbers of atoms in a compound equals to
zero.
Rule 8: The algebraic sum of the oxidation
numbers of the atoms in a polyatomic ion
equals to its charge.

12. Apply
What is the oxidation state of chromium in
CrCl3?
This is a neutral compound so the sum of the oxidation
states is zero. Chlorine has an oxidation state of -1. If
the oxidation state of chromium is n:
n + 3(-1) = 0
n = +3 (Again, don't forget the + sign!)

13. Apply
What is the oxidation state of chromium in
the dichromate ion, CrO2-?
27
The oxidation state of the oxygen is -2, and the sum of
the oxidation states is equal to the charge on the ion.
Don't forget that there are 2 chromium atoms present.
2n + 7(-2) = -2
n = +6

14. Oxidation number
If an atom loses electrons, its oxidation number
increases, so we can say that this atom undergoes
oxidation.
If an atom gains electrons, its oxidation number
decreases, so we can say that the atom undergoes
reduction.
OIL RIG: Oxidation Is Loss; Reduction Is Gain (of
electrons).

15. Redox Reactions
They are chemical reactions through which
atoms gain and lose electrons changing their
oxidation number after the chemical reaction.

16. Apply
Is the following reaction Redox reaction?
Mg + 2HCl MgCl2 + H2
0 +1 -1 +2 -1 0
Mg + 2HCl MgCl2 + H2
Mg loses 2 e
H gains 1 e
Then this reaction is redox reaction

17. Extend
Have ever thought that this occurs in living
cells??
Redox reactions occur in photosynthesis and
cellular respiration.

18. Evaluate
Consider the following reaction:
Fe2O3 + 3CO 2Fe + 3CO2
1. Determine the oxidation number of each of
Fe, O and C before and after the reaction.
2. Deduce if this reaction is a redox reaction.

19. Thank you