Oxides are binary compounds containing oxygen (typically with oxidation state -2) combined with another element. They are fundamental in inorganic chemistry and have important industrial applications.
Nomenclature using prefixes
Multiplicative prefixes indicate the number of atoms of each element: mono-, di-, tri-, tetra-, penta-, hexa-, etc.
Examples:
CO₂: carbon dioxide
Fe₂O₃: diiron trioxide (iron(III) oxide)
N₂O₅: dinitrogen pentoxide
Important notes:
The prefix "mono-" is often omitted in modern names, but it can be used to disambiguate compounds (e.g., carbon monoxide vs carbon dioxide).
Prefix-based names are sometimes traditional; oxidation-state names (using Roman numerals) are preferred for metals with variable oxidation states.
Nomenclature by oxidation state
Oxygen is usually assigned oxidation state -2. The total negative charge from oxygen is compensated by the other element, whose oxidation state is indicated with Roman numerals or numbers in parentheses.
To determine the oxidation state of the other element, multiply -2 by the number of oxygens to get the total negative charge, then divide the positive charge among the atoms of the other element.
For elements that typically have only one oxidation state (alkali metals +1, alkaline earth metals +2, aluminum +3), the oxidation state is often omitted from the name.
Examples:
Fe₂O₃: iron(III) oxide (total O charge -6, Fe each +3)
FeO: iron(II) oxide (total O charge -2, Fe +2)
CuO: copper(II) oxide (Cu +2)
Ag₂O: silver(I) oxide (Ag +1)
CaO: calcium oxide (calcium typically shown without oxidation state)
Peroxides
In peroxides the oxygen has oxidation state -1 and contains an -O-O- bond. They are named as "peroxide" of the element, e.g. sodium peroxide.
Peroxides commonly form with group 1 and group 2 metals and are often unstable; they decompose releasing oxygen or oxidize other substances.
General formula for simple metal peroxides: M₂O₂ (for metals with +1 oxidation state).
Examples:
H₂O₂: hydrogen peroxide (not HO)
Na₂O₂: sodium peroxide
BaO₂: barium peroxide
CaO₂: calcium peroxide
1. Name <b>FeO</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: FeO is a black basic oxide, present in minerals such as wustite.
2. Name <b>Fe₂O₃</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: Fe₂O₃ is known as iron(III) oxide or hematite, a reddish-brown mineral.
3. Name <b>Al₂O₃</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: Al₂O₃ (alumina) is a hard, refractory material used as an abrasive and in ceramics.
4. Name <b>CuO</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: CuO is a black solid used as a pigment and in some battery materials.
5. Name <b>N₂O₅</b>:
(1 point)
a
)
By prefixes
Feedback: N₂O₅ (dinitrogen pentoxide) is a nonmetal oxide that hydrolyzes to nitric acid.
6. Name <b>Na₂O</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: Na₂O is a strongly basic oxide that reacts with water to form sodium hydroxide (NaOH).
7. Name <b>CO₂</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: CO₂ is a colorless gas present in the atmosphere; it plays a key role in the greenhouse effect and photosynthesis.
8. Name <b>CO</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: CO is a colorless, odorless, and highly toxic gas produced by incomplete combustion.
9. Name <b>MnO₂</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: MnO₂ is used in dry cell batteries and as a catalyst in several chemical reactions.
10. Name <b>P₄O₁₀</b>:
(1 point)
a
)
By prefixes
Feedback: P₄O₁₀ (phosphorus pentoxide) is a powerful desiccant that reacts vigorously with water to form phosphoric acid.
11. Name <b>Ag₂O</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: Ag₂O is a dark brown powder used as a reagent in some organic syntheses and in silver-oxide batteries.
12. Name <b>BaO</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: BaO (barium oxide) is a basic oxide that reacts with water to form barium hydroxide; used in glass and ceramic industries.
13. Name <b>SO₃</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: SO₃ is a colorless gas that reacts with water to form sulfuric acid; important industrially.
14. Name <b>Cr₂O₃</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: Cr₂O₃ is a green solid used as a pigment and in metallurgy for chrome plating and polishing.
15. Name <b>CaO</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: CaO (quicklime) is widely used in construction, water treatment, and as an industrial base.
16. Name <b>NO₂</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: NO₂ is a reddish-brown toxic gas found in air pollution and a precursor to acid rain.
17. Name <b>PbO₂</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: PbO₂ is a brown solid used as an oxidizer and in lead-acid battery electrodes.
18. Name <b>SeO₃</b>:
(2 points)
a
)
By oxidation state
b
)
By prefixes
Feedback: SeO₃ is an unstable compound that readily decomposes or hydrolyzes to selenic acid.
19. Write the formulas for the following compounds:
(34 points)
a
)
Vanadium(III) oxide
b
)
Chromium(III) oxide
c
)
Nitrogen(II) oxide
d
)
Iron(III) oxide
e
)
Dinitrogen pentoxide
f
)
Copper(II) oxide
g
)
Carbon dioxide
h
)
Manganese(IV) oxide
i
)
Tetraphosphorus decoxide
j
)
Silver(I) oxide
k
)
Barium oxide
l
)
Sodium oxide
m
)
Carbon monoxide
n
)
Sulfur(VI) oxide
o
)
Chromium(III) oxide
p
)
Calcium oxide
q
)
Nitrogen dioxide
r
)
Lead(IV) oxide
s
)
Selenium(VI) oxide
t
)
Aluminum(III) oxide
Feedback:
20. Name or write the formulas for the following peroxides:
(4 points)