Periodic Relationship among the Oxides of the Elements Li to Cl 39.1Bonding of the Oxides of Periods 2 and 3 Elements 39.2Behaviour of Oxides of Periods

Periodic Relationship aPeriodic Relationship among the Oxides of the mong the Oxides of the

Elements Li to ClElements Li to Cl39.139.1 Bonding of the Oxides of Periods 2 and 3 Bonding of the Oxides of Periods 2 and 3

ElementsElements

39.239.2 Behaviour of Oxides of Periods 2 and 3 Behaviour of Oxides of Periods 2 and 3

Elements in Water, Dilute Acids and Elements in Water, Dilute Acids and Dilute ADilute A

lkalislkalis

3399

39.39.11Bonding of the Bonding of the

Oxides of Oxides of Periods 2 and Periods 2 and

3 Elements3 Elements

IntroductionIntroduction

39.1 Bonding of the Oxides of Periods 2 and 3 Elements (SB p.19)

• The electronegativity value of oxygen is 3.5



• 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



• The compounds formed consist of

positive ions formed the electropositive elements

negative oxide ions

• These oxides are ionic oxides



• When oxygen combines with elements of similar electronegativity values

the oxygen atoms would share electrons with these elements

to form covalent oxides

Nature of BondingNature of Bonding


• The oxides of Periods 2 and 3 elements can be classified into

ionic oxides

ionic oxides with high covalent character

covalent oxides


Periodicity in nature of bonding of the oxides of Periods 2 and 3 elements

Oxide of

Period 2

element

Li2O BeO B2O3

CO

CO2

N2O

NO

NO2

N2O4

N2O5

O2

O3

OF2

Nature of

bonding in

the oxides

Ionic

Ionic with

covalent

character

Covalent

Oxide of

Period 3

element

Na2O

Na2O2

MgO Al2O3 SiO2

P4O6

P4O10

SO2

SO3

Cl2O

Cl2O7

Nature of

bonding in

the oxides

Ionic

Ionic with

covalent

character

Covalent


• 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



• 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



• 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 o

f oxides of Periods 2 and 3 elements

Element

Name of

oxide of

element

Stoichiometric c

omposition of ox

ide of element

Electronic structure

of oxide of element

LithiumLithium

oxideLi2O

BerylliumBeryllium

oxideBeO

Boron Boron oxide B2O3

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

Stoichiometric c

omposition of ox

ide of element


of oxide of element

Carbon

Carbon

monoxideCO

Carbon

dioxideCO2

Nitrogen

Dinitrogen o

xideN2O

Nitrogen

monoxideNO



Element

Name of

oxide of

element

Stoichiometric c

omposition of ox

ide of element


of oxide of element

Nitrogen

Nitrogen

dioxideNO2

Dinitrogen t

etraoxideN2O4

Dinitrogen p

entaoxideN2O5



Element

Name of

oxide of

element

Stoichiometric c

omposition of ox

ide of element


of oxide of element

Oxygen

Oxygen O2

Ozone O3

FluorineOxygen difl

uorideOF2

Sodium

Sodium

monoxide

Na2O

Sodium

peroxideNa2O2



Element

Name of

oxide of

element

Stoichiometric c

omposition of ox

ide of element


of oxide of element

MagnesiumMagnesium

oxide

MgO

AluminiumAluminium o

xide

Al2O3

SiliconSilicon(IV)

oxide

SiO2



Element

Name of

oxide of

element

Stoichiometric c

omposition of ox

ide of element


of oxide of element

Phosphorus

Phosphorus

(III) oxideP4O6

Phosphorus

(V) oxideP4O10



Element

Name of

oxide of

element

Stoichiometric c

omposition of ox

ide of element


of oxide of element

Sulphur

Sulphur dio

xide

SO2

Sulphur trio

xide

SO3


Check Point 39-1Check Point 39-1


Element

Name of

oxide of

element

Stoichiometric c

omposition of ox

ide of element


of oxide of element

Chlorine

Chlorine(I) o

xide

(dichlorine o

xide)

Cl2O

Chlorine(VI

I) oxide

(dichlorine h

eptaoxide)

Cl2O7

39.39.22Behaviour of Oxides of Behaviour of Oxides of

Periods 2 and 3 ElementPeriods 2 and 3 Elements in Water, Dilute Acids s in Water, Dilute Acids

and Dilute Alkalisand Dilute Alkalis

Ionic OxidesIonic Oxides

39.2 Behaviour of Oxides of Periods 2 and 3 Elements in Water, Dilute Acids and Dilute Alkalis (SB p.23)

• 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



• Lithium oxide

reacts vigorously with water to form lithium hydroxide

Li2O(s) + H2O(l) 2LiOH(aq)



• Sodium monoxide

reacts vigorously with water to form sodium hydroxide

Na2O(s) + H2O(l) 2NaOH(aq)



• Sodium peroxide

reacts with water to give sodium hydroxide and hydrogen peroxide

Na2O2(s) + 2H2O(l) 2NaOH(aq) +

H2O2(aq)



• Magnesium oxide

less basic

reacts slightly with cold water and moderately with hot water to form

magnesium hydroxide, which is very slightly soluble



• Magnesium oxide

Magnesium hydroxide solution is a weakly alkaline solution

MgO(s) + H2O(l) Mg(OH)2(s)



• All ionic oxides react with dilute acids to form salts



• 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)

Ionic Oxides with High Ionic Oxides with High Covalent CharacterCovalent Character


• Beryllium oxide and aluminium oxide

ionic oxides with high covalent character

not soluble in water




react with both dilute acids and dilute alkalis to form soluble compounds

amphoteric oxides




BeO(s) + 2H+(aq) Be2+(aq) + H2O(l)

BeO(s) + 2OH–(aq) + H2O(l) [Be(OH) 4]2–(a

q) beryllate ion




Al2O3(s) + 6H+(aq) 2Al3+(aq) + 3H2O

(l)

Al2O3(s) + 2OH–(aq) + 3H2O(l) 2[Al(OH)4]–(aq)

aluminate ion

Covalent OxidesCovalent 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


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• Boron(III) oxide

reacts with water to form boric(III) acid

B2O3(s) + 3H2O(l) 2H3BO3(s)


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• Carbon monoxide

neutral

insoluble in water


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• Carbon dioxide

moderately soluble in cold water

the solution formed is slightly acidic

CO2(g) + H2O(l) H2CO3(aq)


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• Dinitrogen oxide and nitrogen monoxide

neutral

insoluble in water


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• 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


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• Dinitrogen tetraoxide

reacts with water to form nitric(III) acid and nitric(V) acid

N2O4(g) + H2O(l) HNO2(aq) + HNO3(a

q)


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• Dinitrogen pentaoxide

reacts with cold water to form nitric(V) acid

N2O5(s) + H2O(l) 2HNO3(aq)


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• Oxygen

neutral

very slightly soluble in water


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• Oxygen difluoride

colourless gas

hydrolyzes slowly to form oxygen gas and hydrogen fluoride

OF2(g) + H2O(l) 2HF(aq) + O2

(g)


1. Behaviour of Covalent Oxides of Perio1. Behaviour of Covalent Oxides of Period 2 Elements in Water and Dilute Alkalid 2 Elements in Water and Dilute Alkaliss• The reactions can be summarized by the following ionic equations:

B2O3(s) + 6OH–(aq) 2BO3

3–(aq) + 3H2O(l)

CO2(g) + 2OH–(aq) CO3

2–(aq) + H2O(l)



2NO2(g) + 2OH–(aq) NO2

–(aq) + NO3–(aq) + H2O

(l)

N2O4(g) + 2OH–(aq) NO2

–(aq) + NO3–(aq) + H2O

(l)



N2O5(s) + 2OH–(aq) 2NO3

–(aq) + H2O(l)

OF2(g) + 2OH–(aq) 2F–(aq) + O2(g) + H2

O(l)


2. 2. Behaviour of Covalent Oxides of PBehaviour of Covalent Oxides of Period 3 Elements in Water and Dilute Aleriod 3 Elements in Water and Dilute Alkaliskalis• 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)


2. 2. Behaviour of Covalent Oxides of PBehaviour of Covalent Oxides of Period 3 Elements in Water and Dilute Aleriod 3 Elements in Water and Dilute Alkaliskalis• Phosphorus(III) oxide

reacts slowly with cold water to form phosphoric(III) acid

P4O6(s) + 6H2O(l) 4H3PO3(aq)


2. 2. Behaviour of Covalent Oxides of PBehaviour of Covalent Oxides of Period 3 Elements in Water and Dilute Aleriod 3 Elements in Water and Dilute Alkaliskalis• Phosphorus(V) oxide

reacts vigorously with cold water to form phosphoric(V) acid

P4O10(s) + 6H2O(l) 4H3PO4(aq)


2. 2. Behaviour of Covalent Oxides of PBehaviour of Covalent Oxides of Period 3 Elements in Water and Dilute Aleriod 3 Elements in Water and Dilute Alkaliskalis• Sulphur dioxide

react with water to form sulphuric(IV) acid

SO2(g) + H2O(l) H2SO3(aq)sulphuric(IV) acid


2. 2. Behaviour of Covalent Oxides of PBehaviour of Covalent Oxides of Period 3 Elements in Water and Dilute Aleriod 3 Elements in Water and Dilute Alkaliskalis• Sulphur trioxide

react with water to form sulphuric(VI) acid

SO3(g) + H2O(l) H2SO4(aq)sulphuric(VI) acid


2. 2. Behaviour of Covalent Oxides of PBehaviour of Covalent Oxides of Period 3 Elements in Water and Dilute Aleriod 3 Elements in Water and Dilute Alkaliskalis• Chlorine(I) oxide

dissolves in water to form chloric(I) acid (also known as hypochlor

us acid)

Cl2O(g) + H2O(l) 2HOCl(aq) chloric(I) acid


2. 2. Behaviour of Covalent Oxides of PBehaviour of Covalent Oxides of Period 3 Elements in Water and Dilute Aleriod 3 Elements in Water and Dilute Alkaliskalis• 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


2. 2. Behaviour of Covalent Oxides of PBehaviour of Covalent Oxides of Period 3 Elements in Water and Dilute Aleriod 3 Elements in Water and Dilute Alkaliskalis• Ionic equations:

P4O6(s) + 12OH–(aq) 4PO4

3–(aq) + 6H2O(l)

P4O10(s) + 12OH–(aq) 4PO4

3–(aq) + 6H2O(l)



SO2(g) + 2OH–(aq) SO3

2–(aq) + H2O(l)

SO3(g) + 2OH–(aq) SO4

2–(aq) + H2O(l)



Cl2O(g) + 2OH–(aq) 2OCl–(aq) + H2O(l)

Cl2O7(l) + 2OH–(aq) 2ClO4

–(aq) + H2O(l)


Periodicity in the behaviour of oxides of Periods 2elements in water, dilute acids and dilute alkalis

Oxide of

Period 2

element

Li2O BeO B2O3

CO

CO2

N2O

NO

NO2

N2O4

N2O5

O2 OF2

Behaviour

of oxides i

n water

Reacts vi

gorously

with water

to form Li

OH

Does not

react with

water

Reacts

with water

to form

H3BO3,

which is a

very weak

acid

CO:

Insoluble

in water

CO2:

Moderatel

y soluble

in water to

form

H2CO3,

which is a

very weak

acid

N2O and NO:

Insoluble in

water

NO2 and

N2O4: React

with water to

form HNO2

and HNO3

N2O5: Reacts

with cold

water to form

HNO3

Very

slightly

soluble in

water,

does not

react with

water

Hydrolyze

s slowly to

form O2

and an

acidic

solution of

HF


Oxide of Period 2 element

Li2O BeO B2O3

CO

CO2

N2O

NO

NO2

N2O4

N2O5

O2 OF2

Behaviour of oxides in dilute aci

ds

Reacts to form Li+

Reacts to form Be2+

Does not react with dilute acids

Do not react with dilute acids

Do not react with dilute acids






Oxide of

Period 2

element

Li2O BeO B2O3

CO

CO2

N2O

NO

NO2

N2O4

N2O5

O2 OF2

Behaviour

of oxides i

n alkalis

Does not

react with

dilute

alkalis

Reacts to

form

[Be(OH)4]2

–

Reacts to

form BO33–

CO: Does

not react

with dilute

alkalis

CO2:

Reacts to

form CO32–

N2O and NO:

Do not react

with dilute

alkalis

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



Oxide of

Period 2

element

Li2O BeO B2O3

CO

CO2

N2O

NO

NO2

N2O4

N2O5

O2 OF2

Acidic/

basic

nature of

oxides

Alkaline Amphoteric Acidic Acidic Acidic Neutral Acidic



Oxide of Period 3 element

Na2O

Na2O2

MgO Al2O3 SiO2

P4O6

P4O10

SO2

SO3

Cl2O

Cl2O7

Behaviour of oxides in

water

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

Does not react with water

Does not react with water

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



Oxide of

Period 3

element

Na2O

Na2O2

MgO Al2O3 SiO2

P4O6

P4O10

SO2

SO3

Cl2O

Cl2O7

Behaviour

of oxides in

dilute acids

React to

form Na+

Reacts to

form Mg2+

Reacts to

form Al3+

Does not

react with

dilute

acids

Do not

react with

dilute

acids

Do not

react with

dilute

acids

Do not

react with

dilute

acids



Oxide of

Period 3

element

Na2O

Na2O2

MgO Al2O3 SiO2

P4O6

P4O10

SO2

SO3

Cl2O

Cl2O7

Behaviour o

f oxides in

dilute alkali

s

Do not

react with

dilute

alkalis

Does not

react with

dilute

alkalis

Reacts to

form

[Al(OH)4]–

Reacts

with hot

alkalis to

form SiO32–

P4O6:

Reacts

slowly with

cold water

to form

H3PO3

P4O10:

Reacts

vigorously

with cold

water to

form

H3PO4

SO2:

Reacts to

form SO32–

SO3:

Reacts to

form SO42–

Cl2O: Reac

ts to form

OCl– Cl2O7:

Reacts to

form ClO4–


Check Point 39-2Check Point 39-2


Oxide of

Period 3

element

Na2O

Na2O2

MgO Al2O3 SiO2

P4O6

P4O10

SO2

SO3

Cl2O

Cl2O7

Acidic/

basic

nature of

oxides

AlkalineWeakly

acidicAmphoteric

Weakly

acidicAcidic Neutral Acidic

The END

(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 Answer(a) (i) Ionic oxide

(ii) Covalent oxide

(iii) Covalent oxide

(iv) Ionic oxide with covalent

character


(b) Carbon can form two oxides. Name the two oxides and draw their electronic structures.

Answer

Back


(b) Carbon monoxide (CO):

Carbon dioxide (CO2):

(a) Why does silicon(IV) oxide not react with water?

Answer(a) Silicon(IV) oxide does not react with water bec

ause the electronegativity values of silicon and

oxygen are very similar. The Si — O bond can

be considered as nonpolar, so there is no positi

ve centre for the lone pair electrons of the wate

r molecule to attack.


(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


(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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Documents

Periodic Relationship among the Oxides of the Elements Li to Cl 39.1Bonding of the Oxides of Periods 2 and 3 Elements 39.2Behaviour of Oxides of Periods