1. Oxidation Numbers With Manganese Ions Demo
Chapter 10
Oxidation Numbers
With
Manganese Ions Demo

2. Oxidation Number
The oxidation number is the charge on a single atom.

3. Oxidation Number The oxidation number is the charge on a single atom.
Examples:
Na+ (oxidation number = +1)
Clˉ (oxidation number = -1)
Al3+ (oxidation number = +3)
O2ˉ (oxidation number = -2)

4. The periodic table can help to determine oxidation numbers.

5. Determining Oxidation Numbers
Metals form positive ions (7+ is the highest positive oxidation number).
Nonmetals tend to form negative ions.
However other than the noble gases which have an oxidation number of zero, and fluoride (F-) which is always a 1-, all other nonmetals could have positive oxidation numbers as well as the possibility of being negative.

6. We can use the periodic table to “predict” oxidation numbers
If we have the name of the ion a “prediction” is unnecessary.
Potassium ion
Iron (II)
Nitride
We can often predict the range of oxidation numbers of the positive monatomic ions other than groups 1 & 2, Ag, Cd, Zn, and Al.

7. What common ions can Iron form?
Often the electron configuration can help us to understand why certain oxidation numbers form.
Fe +2
Fe +3 7

8. Most transition metal elements have more than one positive ion
Most transition metal elements have more than one positive ion. (However +2 is the most common oxidation number for metal ions).
Fe +2
Fe +3 8

9. What oxidation numbers might we predict for Vanadium?
V = [Ar]4s23d3
V2+ = [Ar]3d3
V5+ = [Ar]
This gives the range of possible oxidation numbers for Vandadium (V2+ through V5+)

10. What oxidation numbers might you predict for Manganese? (Mn)10

11. Mn+2 11

12. The most common oxidation number for metal ions 2+
Mn+2 12

13. The most common oxidation number for metal ions 2+
Mn+2
Mn +7 13

14. Each electron is harder to remove than the one before so sometimes losing electrons can be a gradual process.
Mn +4
Mn +5
Mn +6
Mn+2
Mn +3
Mn +7 14

15. Electrons do not have to be lost one at a time
Electrons do not have to be lost one at a time. The process can be rather random.
Mn +4
Mn +6 Mn
Mn +2
Mn +7 15

16. Demonstration a Mn

17. Demonstration a Mn

18. Determining Oxidation Numbers
What is the oxidation number of nitrogen ([He]2s22p3) within a compound?
Would you predict -3?
Could nitrogen have a positive oxidation number?
How about +3 or maybe +5?
The fact is we can only guess as to what the oxidation number of nitrogen is within a compound unless we have some additional information.

19. Determining Oxidation Numbers
The best way to determine oxidation number of an element is to examine the formula of the compound that the element is in.
We then use some basic rules to help us make a determination as to the oxidation numbers of the elements that make up the compound.

20. Oxidation Number Rules
The oxidation number of all Group 1 metals (+1), Group 2 metals (+2), Ag+, Zn2+, Cd2+, and Al3+ within compounds is a set value.
Hydrogen (H) has two possible oxidation numbers:
+1 when bonded to a nonmetal
-1 when bonded to a metal
The oxidation number of fluorine (F) is always -1.
In a compound the nonmetal closest to fluorine is negative. (Oxygen is the next element most likely to be negative).
The sum of the oxidation numbers of all atoms (ions) in a neutral compound = 0.
The sum of the oxidation numbers of all atoms (ions) in a polyatomic ion = charge on the polyatomic ion.

21. What is the oxidation number of nitrogen?
N2O
N2O is nitrogen (I) oxide
Commonly known as “laughing gas”.

22. Example
NaCl

23. Example
BaH2

24. Example
PO33-

25. Example
FePO3

26. Example
Fe3(PO3)2

27. Homework Worksheet Names and Formulas of Ions (Due tomorrow).
Ions and Oxidation Numbers Worksheet (Due in two days).