5 Chemical Bonds

WAJA F4 Chemistry 2009 Chapter 5: Chemical Bonds

CHAPTER 5 : CHEMICAL BONDS

A Formation of Compounds

Learning Outcomes:You should be able:

explain the stability of noble gases explain the conditions for the formation of chemical bonds state the types of chemical bonds

Activity 1: Formation of chemical bondsChoose the correct answer from the table

1 Noble gases are ………………… gases. They exist as……………………….. gases and

are chemically unreactive . They have ………….………….. octet or ……………..………

electron …………………………..

2 Other atoms besides noble gases tend to achieve the stable electron arrangement

through the formation of …………………………

3 Two types of chemical bonds :

(i) …………………….. bond

- formed when atoms join together by transferring of electrons

(ii) …………………….. bond

- formed when atoms join together by ………………………………..of electrons

B IONIC BONDS

Learning outcomes:You should be able to:

explain the formation of ions write the electron arrangements for the ions formed explain the formation of ionic bonds illustrate electron arrangement of an ionic bond illustrate the formation of ionic bonds

Activity 2 : Formation of ions

1 Underline the correct answer.To achieve a stable electron arrangement :

(i) A metal atom (donates / accepts) electrons , forming a (positive / negative) ion

called cation .

(ii) A (non-metal / metal) atom accepts electrons , forming a (positive / negative) ion

called anion .

2 Complete the diagram below.

1

Sharing ionic stable chemical bondsmonoatomic arrangement inert covalent duplet


(a)

(b)

(Refer to page 84 – 85 - F4 Chemistry text book)

Activity 3 : Formation of ionic bonds

Fill in the blanks with the correct words.1 Formation of ionic compound, sodium chloride ( )

Electron arrangement of sodium atom is .............................................................

A sodium atom ………………….one electron to achieve the ………………

electron arrangement which is 2.8.

Sodium ion, ……..…........ is formed

Electron arrangement of chlorine atom is…………………………………………..

Electron from sodium atom is transferred to a …………………………….…atom

A chlorine atom …………………………electron from sodium atom to

………………………….. the stable electron………………………which is 2.8.8

Chloride ion,………………….. is formed

The sodium ion, and chloride ion, formed are ……………………..to

one another to form an ionic compound …………………….., .

The strong ……………………………….forces between the opposite-charged

ions is called ………………………….bond.

(Refer to page 86 - F4 Chemistry text book)

2 Complete the diagram below.

2


2.8.1 2.8.7 ............. ...............

Sodium atom,Na Chlorine atom,Cl Sodium ion, …… Chloride ion, …..

3(a)

Fill in the blanks with the correct answers.Formation of ionic compound magnesium chloride, MgCl2 .

Electron arrangement of magnesium atom is ..................................................

A magnesium atom ………………….two electrons to achieve the

………………electron arrangement which is, 2.8.

Magnesium ion, ……..…........ is formed

Electron arrangement of chlorine atom is…………………………………………

Electrons from magnesium atom is transferred to two ………………….…

atoms

A chlorine atom …………………………electron from magnesium atom to

…………….. the stable electron …………………………which is 2.8.8.

Chloride ion,………………….. is formed

The magnesium ion,Mg2+ and two chloride ions, formed are ………………

to one another to form an ionic compound …………………………., MgCl2

The strong ……………………………….forces between the opposite-charged

ions is called …………………………..bond

(Refer to page 86 - F4 Chemistry text book)

(b) Complete the diagram below.

(Refer to page 86 - F4 Chemistry text book) C Covalent Bonds

Learning Outcomes: You should be able :

3


state the meaning of covalent bonds explain the formation of covalent bonds illustrate the formation of covalent bonds compare and contrast the formation of ionic and covalent bonds

Activity 4 : Formation of covalent bonds

Fill in the blanks with the correct words.1 Covalent bonds are formed when ..………………… atoms …………………….. electrons

to achieve ……………………. electron arrangements .

2 Types of covalent bonds:-

(i) …………………………………………………………………………………………………

(ii) …………………………………………………………………………………………………

(iii) …………………………………………………………………………………………………

3 A single bond is formed when …………………of electrons is shared between two atoms.

A double bond is formed when ………………..of electrons is shared between two atoms.

A triple bond is formed when ………………….of electrons is shared between two atoms.

4 Formation of hydrogen molecules, H2 :-

A hydrogen atom has ……valence electron, with an electron arrangement of..…….

It needs ……….. more electron to achieve the …………….. electron arrangement

………..hydrogen atoms ………………… one electron each for ………………

Shared-paired electrons forms a …………….. bond in the hydrogen molecule, H2

Single bond holds the two hydrogen atoms together because the shared-pair of

electrons is attracted to the………………….. of both atoms

5 Complete the diagram below.(a)

(b) A covalent bond can be illustrated by using……………………………….

Activity 5 : Formation of covalent bonds

1 Formation of oxygen molecules, O2 :

An oxygen atom has …… valence electron, with an electron arrangement of…..…

4


It needs ……….more electrons to achieve the …………….. electron arrangement

…....oxygen atoms share………pairs of electrons forming a…..……………bond

2(a)

Draw the electron arrangement for the formation of oxygen molecule.[Proton number : O, 8 ;]

(b) Illustrate the formation of oxygen molecule using the Lewis structure.

3 Formation of a nitrogen molecule, N2 :

A nitrogen atom has …… valence electron, with an electron arrangement ..……..

It needs ……… more electrons to achieve the …………….. electron arrangement

………..nitrogen atoms share………………pairs of electrons forming a

……………… covalent bond

4 Draw the electron arrangement for the formation of nitrogen molecule.[Proton number : N, 7]

(b) Illustrate the formation for nitrogen molecule using the Lewis structure.

Activity 6 1 Draw the electron arrangements for the formation of the following ionic compounds:

[Proton number : Li, 3 ; Ca, 20 ; O, 8 ; Cl, 17 ](a) Lithium oxide,

5


(b) Calcium chloride,

2 Draw the electron arrangements for the formation of the following covalent compounds [Proton number : C, 6 ; Cl, 17, : O, 8](a) Tetrachloromethane, CCl4

(b) Carbon dioxide molecule, CO2

3 Complete the table below to compare the characteristics for the formation of ionic and covalent bonds.

Ionic bond Characteristic Covalent bondValence electrons

Electrons involved

ElementsNon-metals atom and non

metal atomsElectron transfer to achieve stable electron arrangement

Bond formation

Particles

D PROPERTIES OF IONIC AND COVALENT BONDING Learning outcomesYou should be able to:

list the properties of ionic compounds. list the properties of covalent compounds explain the differences in the electrical conductivity of ionic and covalent compounds

6


describe the differences in melting and boiling points of ionic and covalent compounds compare and contrast the solubility of ionic and covalent compounds state the uses of covalent compounds as solvents.

Activity 7 : Physical properties of ionic and covalent compounds

1. Complete the table of the properties of ionic and covalent compounds, using the words given in the box :

Ionic compound Properties Covalent compound

Physical states at room temperature

Melting pointsBoiling points

Electrical Conductivity Solubility in water

Solubility in organic solvent

2 Explain why ionic compounds are able to conduct electricity in aqueous solution or in

molten state but not in solid state.

……………………………………………………………………………………………………….

……………………………………………………………………………………………………….

……………………………………………………………………………………………………….

3 Explain why covalent compound do not conduct electricity in all states.

……………………………………………………………………………………………………….

……………………………………………………………………………………………………….

4 Explain why ionic compounds have higher melting points than covalent compounds.

……………………………………………………………………………………………………….

……………………………………………………………………………………………………….

………………………………………………………………………………………………………

5 Example of covalent

compounds ;-.......................................................................................................................

.....................

Uses of covalent compounds as solvent in our daily lives:

………..................................................................................................................................

………………………………………………………………………………………………………

(Refer to page 90 - 91 - F4 Chemistry text book)Activity 8

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conduct electricity in aqueous solution or molten state do not conduct electricity low solid high insoluble soluble solid, liquid, gas


1

Atom A Atom B

(a) Write the electron arrangement for atom A.

………………………………………………………………………………………………..

(b) A and B can form a compound

(i) What type of bond holds atom A and B together ?

…………………………………………………………………………………………..(ii) What will happen to atom A during the formation of the compound with atom

B?

…………………………………………………………………………………………..

(iii) Draw the electron arrangement of the compound formed in (b)(ii).

(iv) State one physical property of the compound formed.

…………………………………………………………………………………………..

(c) Carbon atom, C, with an electron arrangement of 2.4 can combine with atom B to form a compound.

(i) What is the molecular formula of the compound formed?

………………………………………………………………………………………….

(ii) If the relative atomic masses of carbon is 12 and B is 32, what is the relative molecular mass of the compound in c(i).

…………………………………………………………………………………………..

Activity 9

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1 The diagram below shows the proton number and the nucleon number for three atoms of elements, E , G and W. The letters used do not represent the actual symbols of the elements.

(a) The reaction between atoms of element G and W forms an ionic compound whereas the reaction between atoms of element E and W forms a covalent compound.Explain how these ionic and covalent compounds are formed.

Ionic compound

Electron arrangement of an atom of element G is ...................................................

Atom G ………………….one electron to achieve the ………………electron

arrangement which is 2.8

G ion, ……..…........ is formed

Electron arrangement of atom W is…………………………………………..

Electron from atom G is transferred to an atom of…………………

Atom W receives ………….electron from atom G to achieve the ……….…………….

electron arrangement which is 2.8.8

W ion,………………….. is formed

The G ion, ……….. and W ion, ………..formed are …………………………..to one

another to form an …….………compound, ……….

The strong ……………………………….forces between the opposite-charged ions is

called ………………………….. bond.

Covalent bond

Atom E has ……... valence electrons, with an electron arrangement of..……...

It needs ……….. more electrons to achieve the …………….. electron arrangement

One atom of E contributes four electrons for ………………

Atom W has ………valence electrons, with an electron arrangement of…………….

It needs ………….more electron to achieve the……………….electron arrangement

One atom of E share a pair of electrons with ………….atoms of W

Covalent compound of ………………is formed

9

12

E 6

23

G11

35

W17

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5 Chemical Bonds