Chemical Formulas and Compounds
Oxidation Numbers
Monday, November 26
 Take out a sheet of paper, title “Oxidation Numbers”
 Take out your Naming Compounds sheet that you
received before Thanksgiving holiday.
 Hall Pass Policy:
 2 per NINE WEEKS
 Document on Clipboard!
Tuesday, November 27
 1-15 Compound Naming Problems: Any Questions?
 16-30 = Homework Tonight
 Must complete entire sheet to retake Quiz 1 &2
 Take out OXIDATION NUMBER notes from yesterday
 Hall Pass Policy:
 2 per NINE WEEKS
 Document on Clipboard!
Nomenclature QUIZ 1

Write the compound name:
1.
2.
3.
4.
5.

CaBr2
CoF3
SnI4
FeS
Ca(OH)2
Write the formula:
Sodium Iodide
7. Calcium Chloride
8. Potassium Sulfide
9. Sodium Carbonate
10. Calcium Nitrite
6.

Write the nomenclature:
11. Ammonium
12. Sulfate
13. Sulfite
14. Arsenate
15. Phosphate
16. Chlorate
17. Chlorite
18. Hydroxide
19. Tetra20. Penta-
Nomenclature QUIZ 2

Write the compound name:
1.
2.
3.
4.
5.

NaI
CaO
K2O
Ca(OH)2
SO3
Write the formula:
Sodium Hydroxide
7. Lead (II) Nitrate
8. Nitric Acid
9. Barium Dioxide
10. Tricalcium Dinitride
6.

Write the nomenclature:
11. Carbonate
12. Sulfate
13. NO2 ˉ
14. Nitrate
15. Phosphate
16. Hexa17. Nona18. H2SO4
19. Hydrochloric acid
20. Nitric Acid
Nomenclature QUIZ 3

Write the acid name:
1.
2.
3.
4.
5.

HNO2
HClO3
H2SO4
HCl
H2CO3
Write the formula:
Iron (II) Nitrate
7. Sodium Fluoride
8. Carbon Monoxide
9. Potassium Sulfide
10. Iron (III) Oxide
6.

Write the nomenclature:
11. Carbonate
12. Ammonium
13. Hydroxide
14. NO3 ˉ
15. Perchlorate
16. Sulfate
17. Tri18. Octa19. Chlorite
20. PO4 ³ˉ
Oxidation Numbers
 Oxidation Numbers
• the charge that it would have if all the bonds were removed along with the
electron pairs that were shared with the central atom.
• Use to “keep track” of electrons
• In general when assigning oxidation numbers, shared electrons are
assumed to “belong” to the more electronegative atom in each bond
Oxidation numbers of carbon and hydrogen in
ethane (number does not refer to valance electrons)
Oxidation Numbers
 Assigning Oxidation Numbers
• The atoms in a pure element have an oxidation number of zero
• Monatomic ions have an oxidation number equal to the charge of the ion
• The more-electronegative element in a binary compound is assigned a
negative number equal to the charge it would have as an anion. Likewise
for the less-electronegative element.
• Fluorine has an oxidation number of –1 in all of its compounds because it
is the most electronegative element
• Oxygen usually has an oxidation number of –2
• In peroxides, such as H2O2, oxygen’s oxidation number is –1
• In compounds with fluorine, such as OF2, oxygen’s oxidation number is +2
Oxidation Numbers
 Assigning Oxidation Numbers
• Hydrogen has an oxidation number of +1 in all compounds containing
elements that are more electronegative than it; it has an oxidation number
of –1 with metals
• The algebraic sum of the oxidation numbers of all atoms in an neutral
compound is equal to zero
• The algebraic sum of the oxidation numbers of all atoms in a polyatomic
ion is equal to the charge of the ion
• Although rules 1 through 7 apply to covalently bonded atoms, oxidation
numbers can also be applied to atoms in ionic compounds similarly
Oxidation Numbers
 Oxidation Numbers
• Sample Problem
• Assign oxidation numbers to each atom in the following compounds or
ions:
• UF6
• H2SO4
• ClO3
Oxidation Numbers
 Oxidation Numbers
• Sample Problem Solution
• Place known oxidation numbers above the appropriate elements
• Multiply known oxidation numbers by the appropriate number of atoms
and place the totals underneath the corresponding elements
• The sum of the oxidation numbers must equal zero unless there is a
charge associated with the compound
+6 – 1
UF6
+6 – 6
1 6
2
H2 SO 4
2 6
8
+5 2
ClO3–
+5 6
Oxidation Numbers
 Common Oxidation States of Nonmetals
 Pg. 235
Oxidation Numbers
 Oxidation Numbers for Formulas and Names
• Many nonmetals can have more than one oxidation number
• These numbers can sometimes be used in the same manner as ionic
charges to determine formulas (+ -)
• What is the formula of a binary compound formed between sulfur and
oxygen?
• From the +4, +6 oxidation numbers of sulfur, you could predict that sulfur
might form SO2 or SO3
Remember: The more-electronegative
element in a binary compound is
assigned a negative number equal
to the charge it would have as an
anion. Likewise for the lesselectronegative element.
Oxidation Numbers
 Oxidation Numbers for Formulas and Names
• Using oxidation numbers, the Stock system, introduced in the previous
section for naming ionic compounds, can be used as an alternative to the
prefix system for naming binary molecular compounds
Prefix system
Stock system
PCl3
phosphorus trichloride
phosphorus(III) chloride
PCl5
phosphorus pentachloride phosphorus(V) chloride
N2O
dinitrogen monoxide
nitrogen(I) oxide
NO
nitrogen monoxide
nitrogen(II) oxide
Mo2O3
dimolybdenum trioxide
molybdenum(III) oxide
Practice Problems
1. Assign oxidation numbers to each atom in the
following compounds or ions:
a.
b.
c.
d.
e.
f.
g.
h.
HF
CI4
H2O
PI3
CS2
Na2O2
H2CO3
NO2ˉ