A LevelChemistryCIEExam Questions3. Chemical Bonding3.1 Electronegativity & Bonding

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First teaching 2023

First exams 2025

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Electronegativity & Bonding (CIE A Level Chemistry)

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3.1 Electronegativity & Bonding

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3.1 Electronegativity & Bonding

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1a2 marks

This question is about electronegativity.

Define the term electronegativity. 

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1b2 marks

A bond between nitrogen and hydrogen can be represented as straight N with straight delta minus on top space straight H with straight delta plus on top.

i)
In this representation, state the meaning of the symbol δ+.

[1]

ii)
From this bond representation, state what can be deduced about the electronegativity of nitrogen relative to that of hydrogen.

[1]

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1c3 marks

State three factors which affect the electronegativity of an element.

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1d3 marks
i)
Identify the element in Period 4 with the highest electronegativity value.

[1]

ii)
Explain why fluorine is more electronegative than oxygen. 

[2]

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1a2 marks

This question is about electronegativity. 

The electronegativities of some elements are shown in Table 3.1 below. 

Table 3.1

Element Electronegativity 
Li 1.0
H 2.1
C 2.5
N 3.0
Cl 3.0


Define the term electronegativity. 

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1b3 marks

Use Table 3.1 to explain the trend in electronegativity across the Periodic Table.

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1c2 marks

Explain how the carbon-hydrogen bond (such as in CH4) differs from the nitrogen-hydrogen bond (such as in NH3) in terms of the bond polarity.

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1d4 marks

Explain, in terms of electronegativity, why the bonding in ammonia (NH3) is covalent but the bonding in lithium chloride (LiCl) is ionic.

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2a4 marks

Chlorine (Cl) reacts with boron (B) to form boron trichloride (BCl3).

i)
What type of bond is the B-Cl bond?

ii)
How is this bond formed?

iii)
The electronegativities of boron, chlorine and hydrogen are 2.0, 3.2 and 2.2 respectively. Is the B-Cl more or less polar than a B-H bond in borane (BH3)? Explain your answer.

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2b4 marks

Molecules and separate atoms (such as noble gases) are attracted to one another by intermolecular forces. 

i)
What is the strongest type of intermolecular force that takes place between water (H2O) molecules?

ii)
Draw a diagram that illustrates the interaction between two water molecules. Indicate any lone pairs of electrons and partial charges in your diagram.

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2c6 marks

The boiling point of tetrachloromethane (CCl4) is 77 degreeC whereas the boiling point of water (H2O) is 100 degreeC. 

i)
Suggest why the boiling point of H2O is higher than that of CCl4. 

ii)
Predict whether the boiling point of methane (CH4) is higher or lower than the boiling point of CCl4. Explain your answer.

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3a1 mark

Define the term electronegativity.

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3b4 marks

The periodic table displays the chemical elements, arranged in order of increasing atomic number. It is made up of groups and periods of elements.

State and explain the general trend in electronegativity across a period.

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3c4 marks

Chlorine, Cl2, reacts with boron, B, to form boron trichloride, BCl3.

i)
What type of bond is the B-Cl bond?
 [1]
 
ii)
How is this bond formed?
[1]
 
iii)
The electronegativities of boron, chlorine and hydrogen are 2.0, 3.2 and 2.2 respectively. Is the B-Cl more or less polar than a B-H bond in borane, BH3? Explain your answer.
[2]

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1a4 marks
The Pauling electronegativity values of different elements are shown in Fig 3.1.



electronegativity-values

Fig. 3.1

A compound formed from magnesium and oxygen has a different structure to a compound formed from phosphorus and oxygen.

Predict the type of bonds that will occur in each compound. Explain your answer.

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1b2 marks

Explain why the melting point of phosphorus(III) oxide, P4O6, is lower than that of magnesium oxide in terms of their bonding and structure.

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1c1 mark

Phosphorus(III) oxide, P4O6, contains no P–P or O–O bonds.


In the P4O6 molecule, all oxygen atoms are bonded to two other atoms and all phosphorus atoms are bonded to three other atoms.


Sketch a structure for P4O6.

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1d3 marks

Explain the difference in electronegativity shown in Fig. 3.1 between magnesium and calcium.

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