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39
39.1
39.2
Periodic Relationship
among the Oxides of
the Elements Li to Cl
Bonding of the Oxides of Periods 2 and 3
Elements
Behaviour of Oxides of Periods 2 and 3
Elements in Water, Dilute Acids and
Dilute Alkalis
39.1
Bonding of the
Oxides of Periods 2
and 3 Elements
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.19)
Introduction
•
The electronegativity value of oxygen is
3.5
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.19)
Introduction
•
When oxygen combines with elements
having low electronegativity values (e.g.
metals)
 the oxygen atoms would gain the
electrons from the elements
 to form oxide ions
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.19)
Introduction
•
The compounds formed consist of
 positive ions formed the
electropositive elements
 negative oxide ions
•
These oxides are ionic oxides
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.19)
Introduction
•
When oxygen combines with elements of
similar electronegativity values
 the oxygen atoms would share
electrons with these elements
 to form covalent oxides
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.19)
Nature of Bonding
•
The oxides of Periods 2 and 3 elements
can be classified into
 ionic oxides
 ionic oxides with high covalent
character
 covalent oxides
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.20)
Periodicity in nature of bonding of the oxides of Periods 2
and 3 elements
N2O
Oxide of
Period 2
Li2O
BeO
B2O3
element
CO
CO2
NO
O2
NO2
O3
N2O4
OF2
N2O5
Nature of
bonding in
Ionic
the oxides
Oxide of
Period 3
element
Nature of
bonding in
the oxides
Ionic with
covalent
Covalent
character
Na2O
MgO
Na2O2
Ionic
Al2O3
Ionic with
covalent
character
SiO2
P4O6
SO2
Cl2O
P4O10
SO3
Cl2O7
Covalent
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.20)
Nature of Bonding
•
Going across a period from left to right,
the nature of bonding of the oxides
changes from
 ionic bonding
 ionic bonding with covalent character
 covalent bonding
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.20)
Nature of Bonding
•
A number of elements in Periods 2 and 3
form more than one oxide with oxygen
•
Example:
Sodium is a reactive metal
 can form the normal oxide and
peroxide with oxygen
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.20)
Nature of Bonding
•
Elements with electronegativity values
similar to oxygen also form a variety of
oxides
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.20)
Names, stoichiometric composition and electronic structures
of oxides of Periods 2 and 3 elements
Element
Lithium
Beryllium
Boron
Name of
oxide of
Stoichiometric
composition of
element
oxide of element
Lithium
oxide
Beryllium
oxide
Li2O
BeO
Boron oxide B2O3
Electronic structure
of oxide of element
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.20 – 21 )
Names, stoichiometric composition and electronic structures
of oxides of Periods 2 and 3 elements
Element
Name of
oxide of
element
Carbon
monoxide
Stoichiometric
composition of
oxide of element
CO
Carbon
Carbon
dioxide
Dinitrogen
oxide
CO2
N2O
Nitrogen
Nitrogen
monoxide
NO
Electronic structure
of oxide of element
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.21)
Names, stoichiometric composition and electronic structures
of oxides of Periods 2 and 3 elements
Element
Name of
oxide of
Stoichiometric
composition of
element
oxide of element
Nitrogen
dioxide
NO2
Dinitrogen
tetraoxide
N2O4
Nitrogen
Dinitrogen
pentaoxide
N2O5
Electronic structure
of oxide of element
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.21)
Names, stoichiometric composition and electronic structures
of oxides of Periods 2 and 3 elements
Element
Name of
oxide of
Stoichiometric
composition of
element
oxide of element
Oxygen
O2
Ozone
O3
Oxygen
difluoride
OF2
Oxygen
Fluorine
Sodium
Sodium
monoxide
Sodium
peroxide
Na2O
Na2O2
Electronic structure
of oxide of element
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.21)
Names, stoichiometric composition and electronic structures
of oxides of Periods 2 and 3 elements
Element
Magnesium
Aluminium
Silicon
Name of
oxide of
Stoichiometric
composition of
element
oxide of element
Magnesium
oxide
MgO
Aluminium
Al2O3
oxide
Silicon(IV)
oxide
SiO2
Electronic structure
of oxide of element
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.22)
Names, stoichiometric composition and electronic structures
of oxides of Periods 2 and 3 elements
Element
Name of
oxide of
element
Stoichiometric
composition of
oxide of element
Phosphorus
P4O6
(III) oxide
Phosphorus
Phosphorus
P4O10
(V) oxide
Electronic structure
of oxide of element
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.22)
Names, stoichiometric composition and electronic structures
of oxides of Periods 2 and 3 elements
Element
Name of
Stoichiometric
oxide of
element
composition of
oxide of element
Sulphur
SO2
dioxide
Sulphur
Sulphur
trioxide
SO3
Electronic structure
of oxide of element
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.22)
Names, stoichiometric composition and electronic structures
of oxides of Periods 2 and 3 elements
Element
Name of
oxide of
Stoichiometric
composition of
element
oxide of element
Chlorine(I)
oxide
(dichlorine
oxide)
Electronic structure
of oxide of element
Cl2O
Chlorine
Chlorine(VII)
oxide
Cl2O7
(dichlorine
heptaoxide)
Check Point 39-1
39.2
Behaviour of Oxides of
Periods 2 and 3 Elements
in Water, Dilute Acids and
Dilute Alkalis
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides
•
Generally react with water to form
hydroxides
•
As hydroxides are basic oxides
 they neutralize with dilute acids to
form salts
•
Do not react with dilute alkalis
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides
•
Lithium oxide
 reacts vigorously with water to form
lithium hydroxide
Li2O(s) + H2O(l)  2LiOH(aq)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides
•
Sodium monoxide
 reacts vigorously with water to form
sodium hydroxide
Na2O(s) + H2O(l)  2NaOH(aq)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides
•
Sodium peroxide
 reacts with water to give sodium
hydroxide and hydrogen peroxide
Na2O2(s) + 2H2O(l)
 2NaOH(aq) + H2O2(aq)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides
•
Magnesium oxide
 less basic
 reacts slightly with cold water and
moderately with hot water to form
magnesium hydroxide, which is very
slightly soluble
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides
•
Magnesium oxide
 Magnesium hydroxide solution is a
weakly alkaline solution
MgO(s) + H2O(l)  Mg(OH)2(s)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides
•
All ionic oxides react with dilute acids to
form salts
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides
•
The reactions can be summarized by the
following ionic equations:
Li2O(s) + 2H+(aq)  2Li+(aq) + H2O(l)
Na2O(s) + 2H+(aq)  2Na+(aq) + H2O(l)
Na2O2(s) + 2H+(aq)
 2Na+(aq) + H2O2(aq)
MgO(s) + 2H+(aq)  Mg2+(aq) + H2O(l)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides with High
Covalent Character
•
Beryllium oxide and aluminium oxide
 ionic oxides with high covalent
character
 not soluble in water
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides with High
Covalent Character
•
Beryllium oxide and aluminium oxide
 react with both dilute acids and dilute
alkalis to form soluble compounds
 amphoteric oxides
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides with High
Covalent Character
•
Beryllium oxide and aluminium oxide
BeO(s) + 2H+(aq)  Be2+(aq) + H2O(l)
BeO(s) + 2OH–(aq) + H2O(l)
 [Be(OH) 4]2–(aq)
beryllate ion
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.23)
Ionic Oxides with High
Covalent Character
•
Beryllium oxide and aluminium oxide
Al2O3(s) + 6H+(aq)
 2Al3+(aq) + 3H2O(l)
Al2O3(s) + 2OH–(aq) + 3H2O(l)
 2[Al(OH)4]–(aq)
aluminate ion
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
Covalent Oxides
•
Some covalent oxides that are soluble in
water
 react with water to form acids
 react with dilute alkalis
 do not react with dilute acids
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Boron(III) oxide
 reacts with water to form boric(III)
acid
B2O3(s) + 3H2O(l)  2H3BO3(s)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Carbon monoxide
 neutral
 insoluble in water
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Carbon dioxide
 moderately soluble in cold water
 the solution formed is slightly acidic
CO2(g) + H2O(l)  H2CO3(aq)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Dinitrogen oxide and nitrogen monoxide
 neutral
 insoluble in water
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Nitrogen dioxide
 reacts rapidly with cold water to give
a mixture of nitric(III) acid and nitric(V)
acid
2NO2(g) + H2O(l)
 HNO2(aq) + HNO3(aq)
nitric(III) acid
nitric(V)acid
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Dinitrogen tetraoxide
 reacts with water to form nitric(III)
acid and nitric(V) acid
N2O4(g) + H2O(l)
 HNO2(aq) + HNO3(aq)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Dinitrogen pentaoxide
 reacts with cold water to form nitric(V)
acid
N2O5(s) + H2O(l)  2HNO3(aq)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Oxygen
 neutral
 very slightly soluble in water
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
Oxygen difluoride
 colourless gas
 hydrolyzes slowly to form oxygen gas
and hydrogen fluoride
OF2(g) + H2O(l)  2HF(aq) + O2(g)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
The reactions can be summarized by the
following ionic equations:
B2O3(s) + 6OH–(aq)
 2BO33–(aq) + 3H2O(l)
CO2(g) + 2OH–(aq)
 CO32–(aq) + H2O(l)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
The reactions can be summarized by the
following ionic equations:
2NO2(g) + 2OH–(aq)
 NO2–(aq) + NO3–(aq) + H2O(l)
N2O4(g) + 2OH–(aq)
 NO2–(aq) + NO3–(aq) + H2O(l)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.24)
1. Behaviour of Covalent Oxides of Period 2
Elements in Water and Dilute Alkalis
•
The reactions can be summarized by the
following ionic equations:
N2O5(s) + 2OH–(aq)
 2NO3–(aq) + H2O(l)
OF2(g) + 2OH–(aq)
 2F–(aq) + O2(g) + H2O(l)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Silicon(IV) oxide
 does not react with water
 weakly acidic
 reacts with hot alkalis to form silicates(IV)
SiO2(s) + 2NaOH(aq)
 Na2SiO3(aq) + H2O(l)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Phosphorus(III) oxide
 reacts slowly with cold water to form
phosphoric(III) acid
P4O6(s) + 6H2O(l)  4H3PO3(aq)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Phosphorus(V) oxide
 reacts vigorously with cold water to
form phosphoric(V) acid
P4O10(s) + 6H2O(l)  4H3PO4(aq)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Sulphur dioxide
 react with water to form sulphuric(IV)
acid
SO2(g) + H2O(l)  H2SO3(aq)
sulphuric(IV) acid
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Sulphur trioxide
 react with water to form sulphuric(VI)
acid
SO3(g) + H2O(l)  H2SO4(aq)
sulphuric(VI) acid
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Chlorine(I) oxide
 dissolves in water to form chloric(I)
acid (also known as hypochlorus acid)
Cl2O(g) + H2O(l)  2HOCl(aq)
chloric(I) acid
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Chlorine(VII) oxide
 dissolves in water to form a very
strong acid called chloric(VII) acid
(also known as perchloric acid)
Cl2O7(l) + H2O(l)  2HClO4(aq)
chloric(VII) acid
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Ionic equations:
P4O6(s) + 12OH–(aq)
 4PO43–(aq) + 6H2O(l)
P4O10(s) + 12OH–(aq)
 4PO43–(aq) + 6H2O(l)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Ionic equations:
SO2(g) + 2OH–(aq)
 SO32–(aq) + H2O(l)
SO3(g) + 2OH–(aq)
 SO42–(aq) + H2O(l)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.25)
2. Behaviour of Covalent Oxides of Period 3
Elements in Water and Dilute Alkalis
•
Ionic equations:
Cl2O(g) + 2OH–(aq)
 2OCl–(aq) + H2O(l)
Cl2O7(l) + 2OH–(aq)
 2ClO4–(aq) + H2O(l)
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.26)
Periodicity in the behaviour of oxides of Periods 2
elements in water, dilute acids and dilute alkalis
N2O
Oxide of
Period 2
element
Li2O
BeO
B2O3
CO
CO2
NO
NO2
O2
OF2
Very
slightly
soluble in
water,
does not
react with
water
Hydrolyze
s slowly to
form O2
and an
acidic
solution of
HF
N2O4
N2O5
Behaviour
of oxides
in water
Reacts
vigorously
with water
to form
LiOH
Does not
react with
water
Reacts
with water
to form
H3BO3,
which is a
very weak
acid
CO:
Insoluble
in water
N2O and NO:
Insoluble in
water
CO2:
Moderatel
y soluble
in water to
form
H2CO3,
which is a
very weak
acid
NO2 and
N2O4: React
with water to
form HNO2
and HNO3
N2O5: Reacts
with cold
water to form
HNO3
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.26)
Periodicity in the behaviour of oxides of Periods 2
elements in water, dilute acids and dilute alkalis
Oxide of
Period 2
element
Behaviour
of oxides
in dilute
acids
Li2O
Reacts to
form Li+
BeO
Reacts to
form Be2+
B2O3
Does not
react with
dilute
acids
CO
CO2
Do not
react with
dilute
acids
N2O
NO
NO2
N2O4
N2O5
Do not react
with dilute
acids
O2
Does not
react with
dilute
acids
OF2
Does not
react with
dilute
acids
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.26)
Periodicity in the behaviour of oxides of Periods 2
elements in water, dilute acids and dilute alkalis
N2O
Oxide of
Period 2
element
Li2O
BeO
B2O3
CO
CO2
NO
NO2
O2
OF2
N2O4
N2O5
Does not
react with
dilute
alkalis
Behaviour
of oxides
in alkalis
Reacts to
form
[Be(OH)4]2
–
Reacts to
form BO33–
CO: Does
not react
with dilute
alkalis
N2O and NO:
Do not react
with dilute
alkalis
CO2:
Reacts to
form CO32–
NO2 and
N2O4: React
to form NO2–
and NO3–
N2O5: Reacts
to form NO3–
Does not
react with
dilute
alkalis
Reacts to
form F–
and O2
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.26)
Periodicity in the behaviour of oxides of Periods 2
elements in water, dilute acids and dilute alkalis
N2O
Oxide of
Period 2
element
Li2O
BeO
B2O3
CO
CO2
NO
NO2
O2
OF2
Neutral
Acidic
N2O4
N2O5
Acidic/
basic
nature of
oxides
Alkaline
Amphoteric
Acidic
Acidic
Acidic
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.27)
Periodicity in the behaviour of oxides of Periods 3
elements in water, dilute acids and dilute alkalis
Oxide of
Period 3
element
Behaviour
of oxides in
water
Na2O
Na2O2
MgO
Na2O:
Reacts
vigorously
with water
to form
NaOH
Na2O2:
Reacts
with water
to form
NaOH and
H2O2
Reacts
slightly
with cold
water and
moderately
with hot
water to
form a
weakly
alkaline
solution of
Mg(OH)2
Al2O3
Does not
react with
water
SiO2
Does
not
react
with
water
P4O6
P4O10
SO2
SO3
Cl2O
Cl2O7
P4O6:
Reacts
slowly with
cold water
to form
H3PO3
P4O10:
Reacts
vigorously
with cold
water to
form
H3PO4
SO2:
Reacts
with water
to form
H2SO3
SO3:
Reacts
with water
to form
H2SO4
Cl2O:
Dissolves
in water to
form HOCl
Cl2O7:
Dissolves
in water to
form
HClO4
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.27)
Periodicity in the behaviour of oxides of Periods 3
elements in water, dilute acids and dilute alkalis
Oxide of
Period 3
element
Behaviour
of oxides in
dilute acids
Na2O
Na2O2
React to
form Na+
MgO
Reacts to
form Mg2+
Al2O3
Reacts to
form Al3+
SiO2
Does not
react with
dilute
acids
P4O6
SO2
Cl2O
P4O10
SO3
Cl2O7
Do not
react with
dilute
acids
Do not
react with
dilute
acids
Do not
react with
dilute
acids
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.27)
Periodicity in the behaviour of oxides of Periods 3
elements in water, dilute acids and dilute alkalis
Oxide of
Period 3
element
Na2O
Na2O2
Do not
react with
dilute
alkalis
Behaviour
of oxides in
dilute
alkalis
MgO
Does not
react with
dilute
alkalis
Al2O3
Reacts to
form
[Al(OH)4]–
SiO2
Reacts
with hot
alkalis to
form
SiO32–
P4O6
SO2
Cl2O
P4O10
SO3
Cl2O7
P4O6:
Reacts
slowly with
cold water
to form
H3PO3
SO2:
Reacts to
form SO32–
Cl2O:
Reacts to
form OCl–
Cl2O7:
Reacts to
form ClO4–
P4O10:
Reacts
vigorously
with cold
water to
form
H3PO4
SO3:
Reacts to
form SO42–
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.27)
Periodicity in the behaviour of oxides of Periods 3
elements in water, dilute acids and dilute alkalis
Oxide of
Period 3
element
Acidic/
basic
nature of
oxides
Na2O
Na2O2
Alkaline
MgO
Al2O3
SiO2
Weakly
acidic
Amphoteric
Weakly
acidic
P4O6
SO2
Cl2O
P4O10
SO3
Cl2O7
Acidic
Neutral
Acidic
Check Point 39-2
The END
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.22)
(a) To which type of oxide does each of the following
oxides belong?
(i) Magnesium oxide
(ii) Nitrogen monoxide
(iii) Silicon dioxide
(iv) Aluminium oxide
(a) (i) Ionic oxide
(ii) Covalent oxide
(iii) Covalent oxide
(iv) Ionic oxide with covalent character
Answer
39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.22)
(b) Carbon can form two oxides. Name the two oxides and
draw their electronic structures.
Answer
(b) Carbon monoxide (CO):
Carbon dioxide (CO2):
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39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.27)
(a) Why does silicon(IV) oxide not react with water?
(a) Silicon(IV) oxide does not react with water
because the electronegativity values of silicon
and oxygen are very similar. The Si — O bond
can be considered as nonpolar, so there is no
positive centre for the lone pair electrons of the
water molecule to attack.
Answer
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.27)
(b) Complete and balance the following equations:
(i) K2O(s) + H2O(l) 
(ii) Na2O2(s) + HCl(aq) 
(iii) Al2O3(s) + H2SO4(aq) 
(iv) P4O10(s) + NaOH(aq) 
(v) SO3(g) + NaOH(aq) 
Answer
39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids
and Dilute Alkalis (SB p.27)
(b) (i) K2O(s) + H2O(l)  2KOH(aq)
(ii) Na2O2(s) + 2HCl(aq)  2NaCl(aq) + H2O2(aq)
(iii) Al2O3(s) + 3H2SO4(aq)  Al2(SO4)3(aq) + 3H2O(l )
(iv) P4O10(s) + 12NaOH(aq)  4Na3PO4(aq) + 6H2O(l)
(v) SO3(g) + 2NaOH(aq)  Na2SO4(aq) + H2O(l)
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