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CHAPTER 5: CHEMICAL BOND

CHEMICAL

BOND

Formation of

compoundIonic bond

Covalent bond

Ionic compound and

covalent compound.

1. What is the relation between valence

electrons and the reaction of atoms ?

2. Why atoms of group 18 are inert

chemically?

3. What is happening to the valence

electrons of an atom before the reaction?

1. What happen to the electrons of atoms

when the formation of bond occurs?

2 .Define ionic bond.

3. Named 3 ionic substances and then

draw electron arrangement diagram to

describe the formation of the substances.

1. What happen to the electrons of atoms

when the formation of covalent bond

occurs?

2. Define covalent bond.

3. Named 3 covalent compound and then

draw electron arrangement diagram to

describe the formation of those

compound.

1. Compare the properties of ionic and

covalent substances.

2. Give explanation:

i) melting point of ionic compound is

higher then covalent compound.

ii) Ionic compound are able to

conduct electricity in smelting but

covalent compound are not.

3. Why covalent compound always used

as solvent in industry?.

5.15.2

5.35.4

2

A.Fill in the blank.

1. Noble gases have stable o……..… or d……….... electron arrangements.

2. Atoms of other elements tend to achieve the stable e…………. arrangement

through the formation of chemical bonds.

3. Chemical bonds are formed when two or more a………… of elements bond

together.

4. Chemical bonds can be formed by the t……………. of electrons or s…………. of

electrons.

5. When atoms join together by transferring of electrons, an i……… bond is formed.

6. A c…………. bond is formed when atoms are join together by sharing electrons.

Electron arrangement of neon atom = 2.8

Electron arrangement of helium atom = 2

Helium atom have been achieved the stable

electron arrangement (duplet)

Neon atom have been achieved the stable

electron arrangement (octet)

FORMATION OF

COMPOUND

Why inert gases are stable?

Atom of noble gas achieved the stable electron arrangement (duplet

or octet). Therefore no need to donate, accept or sharing electron

with other atoms. Thus cannot react with other atoms.

Why other atoms of other

elements are unstable?

The Atoms are not achieved the stable electron arrangement (duplet or octet) .

Therefore the atoms should donate, accept or share electron with other atoms

to achieved stable electron arrangement and react to form ionic or covalent

compound.

T. 5.1

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7. In chemical reaction,

Neutral donates electron Positive ion

atom (C…..……)

Metal atom

Neutral accepts electron Negative ion

Atom (A……….)

Non-metal atom

8. Examples:

(i) Sodium (Proton number =11)

Electron arrangement : ……………….

+

donates one electron

Sodium atom, Na Sodium ion, Na+

Charge of 11 protons = ………….. Charge of 11 protons = …………….

Charge of 11 electrons = ………...... Charge of 10 electrons = …………….

Total charge = ………….. Total charge = …………….

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(ii) Chloride (Proton number = 17)

Electron arrangement : ……………….

_

accept one electron

Chlorine atom, Cl Chlorine ion, Cl-

Charge of 17 protons = ………….. Charge of 17 protons = …………….

Charge of 17 electrons = ………...... Charge of 18 electrons = …………….

Total charge = ………….. Total charge = …………….

IONIC BOND

Ion formation

Formation of

ionic bond

Definition

The bond that formed due to

electrostatic force between

positively charge ion and

negative charge ion.

Occurs when

metal and non-

metal reacted.

Examples:

MgO ,

AlCl3 ,

Li2O

Na - e Na+

Sodium atom expel one electron to achieve

stable electron arrangement (octet) to form

positively charge of sodium ion.

Cl + e Cl-

Chlorine atom accept one electron to

achieve stable electron arrangement (octet)

to form negative charge of chloride ion.

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Sodium atom donate one electron to chlorine atom to achieve stable electron

arrangement to form sodium ion. Chlorine atom accept one electron from sodium

atom to achieve the stable electron arrangement to form chloride ion . Positively

charge sodium ion and negatively chloride ion are attract by strong electrostatic force.

Na Cl Na+ Cl-

2.8.1 2.8.7 2.8 2.8.8

T. 5.2

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9. Ionic bonds are formed when atoms of metal elements d…………… electron to

atoms of non-metal elements to achieve the s…………. electron arrangement like

n………. gases.

10. I…………. compounds are compound that are formed through ionic bonds.

11. Examples:

(i) Sodium chloride

Sodium Chlorine Sodium chloride

+ _

+

Na Cl Na+ Cl-

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

Sodium atom has …………. valence electron.

Sodium atom …………… one electron to form sodium ion, Na+ and achieve a

stable …………… arrangement.

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

Chlorine atom has …………. valence electron.

Chlorine atom …………… one electron to form chloride ion, Cl- and achieve the

stable …………electron arrangement.

The sodium ion, Na+ and chloride ion, Cl- formed are attracted to one another with

strong force to form a solid sodium chloride, NaCl compound. The attractive

………………..force between the ions is called an ionic bond or electrovalent

bond.

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(ii) Magnesium oxide

Proton number of magnesium = 12

Proton number of oxygen = 8

Draw a diagram to show the bonding formed between elements magnesium and

oxygen.

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

Magnesium atom has …………. valence electron.

Magnesium atom …………… two electron to form magnesium ion, Mg2+ and

achieve a stable …………… arrangement.

Electron arrangement of oxygen atom is ...................

Oxygen atom has …………. valence electron.

Oxygen atom …………… two electron to form oxide ion, O2- and achieve the

stable …………electron arrangement.

The magnesium ion, Mg2+ and oxide ion, O2- formed are attracted to one another

with strong force to form a solid magnesium oxide, MgO compound. The

attractive ………………..force between the ions is called an ionic bond or

electrovalent bond.

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(iii) Magnesium fluoride

Proton number of magnesium = 12

Proton number of fluorine = 9

Draw a diagram to show the bonding formed between elements magnesium and

fluorine.

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

Magnesium atom has …………. valence electron.

Magnesium atom …………… two electron to form magnesium ion, Mg2+ and

achieve a stable …………… arrangement.

Electron arrangement of fluorine atom is ...................

Fluorine atom has …………. valence electron.

Fluorine atom accept ……… electron to form fluoride ion, F- and achieve the

stable …………electron arrangement.

One magnesium atom donates two electron to …………….. fluorine atoms.

The magnesium ion, Mg2+ and fluoride ion, F- formed are attracted to one another

with strong force to form a solid magnesium fluoride, MgCl2 compound. The

attractive ………………..force between the ions is called an ionic bond or

electrovalent bond.

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12. Ionic bond is usually formed by atoms from group …..., ……. and ………(metal)

with group ……., ……… and ………(non-metal)

KOVALENT BOND

Definition

Bond occurs due to

sharing of electron

between atoms.

Formation of bond

Other eg:

N2

NH3

H2O .

CH4

CO2Eg

Occurs when non-metal

and non-metal reacted.

Triple bond3

Double bond2

Single bond1

Type of covalent

bond

No. of electron

pair.

Cl Cl Cl-Cl or Cl2OR

Lewis Structure

2 atoms of chlorine sharing a pair of electron to achieve

stable electron arrangement to form chlorine molecule.

A single covalent bond is formed.

T. 5.3

13. Covalent bonds are formed when non-metal atoms …………………. electron to

achieve ………………. electron arrangement.

14. Normally atoms from group ………, ………, ………. and ……… share valence

electrons between them.

15. Types of covalent bonds include …………….. bonds, ………….. bonds or

………… bonds.

16. A single bond is a covalent bond formed when a ………….. of electrons is shared

between two atoms.

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17. Double bonds formed when …………. pairs of electron are shared between two

atoms.

18. Triple bonds formed when …………. pairs of electron are shared between two

atoms.

19. Examples:

20. (i) Hydrogen molecule.

Hydrogen atom has ……….. valence electron and needs one more electron to

achieve the duplet …………………...

Two hydrogen atoms contribute ………….. electron each for sharing, forming

a single bond in the hydrogen molecule, H2

Both hydrogen atoms achieve a stable ………….. arrangement of electron.

+

Hydrogen atom, H Hydrogen atom, H Hydrogen molecule, H2

The formation of a covalent bond can be illustrated using the …………

structure.

H + H H H or H – H

(ii) Oxygen molecule

The electron arrangement of oxygen atom is ……………….

Oxygen atom has ……….... valence electron and needs …………. electrons

to achieve the ……………. electron arrangement

Two oxygen atoms share ………….. pairs of electron, forming a double bond

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Draw a diagram to show the bonding formed in oxygen molecule.

Oxygen atom, O Oxygen atom, O Oxygen molecule, O2

Lewis structure:

O + O O O or O = O

(iii) Nitrogen molecule

The electron arrangement of nitrogen atom is ……………….

Nitrogen atom has ……….... valence electron and needs …………. electrons

to achieve the ……………. electron arrangement

Two oxygen atoms share ………….. pairs of electron, forming a triple bond

Draw a diagram to show the bonding formed in nitrogen molecule.

Nitrogen atom, N Nitrogen atom, N Nitrogen molecule, N2

Lewis structure:

N + N N N or N = N

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PROPERTIES OF IONIC AND

COVALENT COMPOUND

Comparison of properties

Uses

Solvent of food

substance Solvent for chemical

substance

Cleaning process

Eg.

Eg.

Eg.

Demonstration

and explanation

to the properties.

1. Consist of giant molecule

solid

2. High melting and boiling

point

3. Not vapourize

4. Non soluble in water and

organic solution

5. Insulator of electric

1. Consist of simple

molecule

2. Liquid and gas

low melting and boiling

point

3. Vapourize

4. Soluble in organic solvent

5. Insulator of electric

(No free moving ion,

Consist of free molecules)

1. Consist of ions

2. Solid

3. High melting and boiling

point

4. Not vapourize

5. Soluble in water

6. Conductor of electric in

smelting and aqueous

solution (due to free

moving ions)

GIANT MOLECULESIMPLE MOLECULE

COVALENT COMPOUNDIONIC COMPOUND

T. 5.4

21. Comparison between the formation of ionic and covalent bonds.

Characteristic Ionic Bond Covalent Bond

Types of elements

involved

Between metals

(group…………..…..) and

non-metals(group……….)

Between non-metal and

non-metals

(group…………….…)

Bond formation

Electron transfer.

Metal atoms ……………

electron and non-metal

atoms …………………

electron.

Sharing electron.

……………… of

electrons are shared by the

same or different non-

metal atoms.

Strength of bond

Strong ……………………

force.

Strong ………………….

Bond

Particles in the compound

formed

Metal: ……………….. ion

Non-metal:……………ion Neutral ………………….

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22. The Properties of Ionic and Covalent Compound.

Properties Ionic Compound Covalent Compound

Melting and boiling point

Have ……... melting point

and ………. boiling pont

because:

Positive ions and

negative ions are held

together by strong

…………….… forces

Large amount of

energy is needed to

overcome the

…………. forces.

Exist as ……………… at

room temperature.

Have ………….. melting

and boiling point because:

The molecule in

covalent compound

are held together by

…………………..

intermolecular

forces.

…………… heat

energy is needed to

overcome these

forces.

Exist as solids, liquids or

………………

Electrical conductivity Does not conduct

electricity when in

……………. state but can

conduct electricity in

………….. solution or

…………. state because:

In solid, ions are

………… in positions

and do not ………….

freely.

In aqueous solution or

molten state, ions are

………… to move

Do not ………………..

electricity in any state

because covalent

compound consists of

neutral ………………….

Solubility Most ionic compounds are

…………….. in water but

are ………………… in

organic solvents.

Most covalent compounds

are ………………… in

water but can …………….

in organic solvents.

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Properties Ionic Compound Covalent Compound

Votality ………… because ions are

held together by strong

electrostatic forces.

High ……………. because

of the weak ………………

forces.

B. Objective questions

1. The table shows the number of protons, electrons and neutrons of atoms Q and R.

Atom Number

Proton Electron Neutron

Q 11 11 12

R 12 12 12

Which of the following is true about atoms Q and R?

A. R can form a diatomic molecule

B. Q and R have the same chemical properties

C. R reacts with Q to form an ionic compound

D. Q reacts with water to release hydrogen

2. The diagram shows the electron arrangement of a compound formed between

atoms P and Q.

Which of the following statements is true about the compound?

A. It is an ionic compound

B. The compound is formed by covalent bonds

C. The compound has a high boiling point

D. The compound is formed by electron transfer

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3. The diagram shows the electron shells in the substance formed between atoms of

hydrogen and Y.

What is the electron configuration of atom Y?

A. 2.4 C. 2.8.4

B. 2.8 D. 2.8.8

4. Which of the following pairs of physical properties of sodium chloride is true?

Solubility Electrical conductivity

in water when molten

A. Soluble Conducting

B. Soluble Not conducting

C. Insoluble Conducting

D. Insoluble Not conducting

5. An atom of element X has 4 shells containing electrons.

When element X reacts with chlorine, a compound with formula XCl is formed.

Which of the following is element X?

Given that the atomic number of Na = 11, Si = 14, K = 19, Ca =20

A. Calcium C. Sodium

B. Potassium D. Silicone

6. The figure shows the electron arrangement of an atom of element X

The atom of element X can form a covalent bond with another atom through the

A acceptance of two electrons

B donation of two electrons

C sharing of two pairs of electrons

D elimination of three pairs of electrons

X

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7. Electron arrangement for P atom is 2.8.3 and R atom has six valence electrons.

Which of the following pairs of formula compound and type of compound is true?

Formula compound Type of compound

A. P2R3 Kovalen

B. P2R3 Ion

C. P3R2 Kovalen

D. P3R2 Ion

8. The Figure shows the information for element X and element Y.

and

Which of the following electron arrangement of the compound formed is correct when element X

react with element Y?

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X 3

16

Y 8

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9. The table shows the proton number of elements V, W, X and Y.

Element V W X Y

Proton number 8 3 11 16

Which of the following pairs will form a compound with lowest melting point?

A. X and Y

B. V and Y

C. V and X

D. V and W

10. The table shows elements E, G, J, L and M with their respective proton number.

Which of the following pairs of element form a compound that insoluble in water?

Element E G J L M

Proton number 6 8 9 11 12

A E dan J

B J dan L

C G dan L

D G dan M

C. Structure Questions

1. Figure 1 shows part of the Periodic Table of Elements.

(a) Write the electron configuration for the Mg atom.

…………………………………………………………………………………

[1 mark]

(b) (i) Write the chemical equation for the reaction between aluminium and

oxygen gas.

…………………………………………………………………………….

[1 mark]

FIGURE 1

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(ii) Briefly state the electron transfer in the bond formation between

aluminium and oxygen.

…………………………………………………………………………….

[2 mark]

2. (a) (i) The electron arrangement for argon is 2.8.8.

Why is this element very stable and not reactive?

……………….………………………………………………………...…

[1 mark]

(ii) Name one other element that has the same stability as argon.

……………………………………………………………………………

[1 mark]

(b) Atoms of both sodium and chlorine are unstable.

They react to form an ionic compound which is more stable.

Diagram 1.1 shows a sodium chloride compound, NaCl, that is produced by

the formation of an ionic bond between a sodium ion, Na+, and a chloride

ion, Cl-

DIAGRAM 1.1

(i) How are a sodium ion and a chloride ion formed from their respective

atoms?

Sodium ion: ……………………………………………………………

Chloride ion:……………………………………………………………

[2 marks]

(ii) Name the force that exists between these ions in the compound.

……………………………………………….………………………….

[1 mark]

(iii) The melting point of sodium chloride, NaCl, is 108 oC and its boiling

point is 1 413 oC.

What will happen to the ions in this compound at 900 oC?

…………………………………………………………………………...

[1 mark]

(iv) Give one reason for your answer in 2(b)(iii).

…………………………………………………………………………...

[1 mark]

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(c) Diagram 1.2 shows the proton number and the nucleon number for two

elements, X and Y.

The letters used do not represent the actual symbols of the elements.

DIAGRAM 1.2

Draw a diagram to show the bonding formed between elements X and Y.

[3 marks]

D. Essay Questions

1. Figure 1 shows the chemical symbols which represent three elements, X, Y and Z.

FIGURE 1

(a) (i) Write the electron arrangement of atoms X and Y.

[2 marks]

(ii) State the number of neutrons in an atom of element Z and write the

symbol for an isotope of element Z

[2 marks]

(b) The reaction between atoms of X and Y forms an ionic compound whereas

the reaction between atoms of Y and Z forms a covalent compound.

Based on the above statement, explain how these ionic and covalent

compound are formed.

[8 marks]

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2. (a) Figure 2 shows the electron arrangement of a molecule PQ2.

These letters are not the actual symbols of the elements.

FIGURE 2

Based on Figure 2, write the electron arrangement for atoms of element P and

element Q.

Explain the position of element Q in the Periodic Table of the Elements.

[6 marks]

(b) Table 1 shows the electron arrangement for atoms W, X and Y.

These letters are not the actual symbols of the elements.

Element Electron arrangement

W 2.4

X 2.8.7

Y 2.8.8.2

TABLE 1

Using the information in Table 1, explain how two compounds can be formed

from these elements based on their electron arrangements.

The two compounds should have different bond types

[10 marks]