A LevelChemistryCIEExam Questions1. Atomic Structure1.4 Ionisation Energy

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First teaching 2023

First exams 2025

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Ionisation Energy (CIE A Level Chemistry)

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1.4 Ionisation Energy

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1.4 Ionisation Energy

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11 mark

Which of the following statements describes first ionisation energy?

  • The energy required to remove one mole of electrons from one mole of gaseous atoms.

  • Mg → Mg+ + e-

  • Mg+ → Mg2+ + e-

  • The amount of energy required to remove one mole of electrons from one mole of gaseous ions of an element to form one mole of gaseous 2+ ions

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21 mark

Which is the correct equation for the first ionisation energy for magnesium?

  • Mg → Mg+ + e-

  • Mg+ (g) → Mg2+ (g) + e-

  • Mg (g) → Mg+ (g) + e-

  • Mg+ → Mg2+ + e-

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31 mark

Why is the second ionisation energy of magnesium higher than the first ionisation energy?

  • Less shielding

  • Ionic radius increases

  • Nuclear charge is increasing

  • Greater attraction between positive nucleus and outer electron

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4
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The first five ionisation energies of an element are shown below.

What element could this ionisation energy graph belong to?

successive-ionisation-energy

  • N

  • P

  • Al

  • Na

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5
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Which statement does not explain the increase in ionisation energy across a period?

  • Nuclear charge increases

  • Atomic radius decreases

  • Shielding remains constant

  • Number of electrons increase

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11 mark

The second ionisation energy of magnesium is 1451 kJ mol-1. 

Which equation correctly represents this statement?

  • Mg+ (g) → Mg2+ + e-          ΔHӨ = -1451 kJ mol-1

  • Mg+ (g) → Mg2+ + e-          ΔHӨ = +1451 kJ mol-1

  • Mg (g) → Mg2+ + 2e-         ΔHӨ  = +1451 kJ mol-1

  • Mg (g) → Mg+ + e-            ΔHӨ = -1451 kJ mol-1

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21 mark

The successive ionisation energies of element X are shown in the table below. Which group of the periodic table does element X belong to?

Ionisation number of X

1

2

3

4

5

6

7

8

Ionisation energy (kJ mol-1)

1314

3388

5301

7469

10989

13327

71337

84080

  • 3

  • 4

  • 5

  • 6

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31 mark

X, Y and Z  are consecutive elements in the third Period of the Periodic Table. Element Y has the highest first ionisation energy and also the lowest melting point of these three elements. 

What could be the identities of X, Y and Z?

  • silicon, phosphorus, sulfur 

  • sodium, magnesium, aluminium

  • aluminium, silicon, phosphorus

  • magnesium, aluminium, silicon

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41 mark

Successive ionisation energies for an element, Y, are shown in the table below.

Electrons removed

1st

2nd

3rd

4th

5th
Ionisation energy / kJ mol-1

736

1450

7740

10500

13600

What is the most likely formula for the ion of Y?

  • Y+

  • Y2+

  • Y3+

  • Y4+

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51 mark

Values for the successive ionisation energies for an unknown element are given in the table below.

First ionisation energy / kJ mol-1

Second ionisation energy / kJ mol-1

Third ionisation energy / kJ mol-1

Fourth ionisation energy / kJ mol-1

420

3600

4400

5900

In which group of the periodic table would the unknown element be found?

  • 1

  • 2

  • 13

  • 14

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11 mark

Element X is in period 2 and has the first seven ionisation energies in kJ mol-1 as shown.

1300

3380

5330

7460

11 010

13 320

71 200

What is the electronic configuration of element X?

  • 1s2 2s2 2p4

  • 1s2 2s2 2p2

  • 1s2 2s2 2p3

  • 1s2 2s2 2p6

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21 mark

For the successive ionisation energies of oxygen, where would the highest jump be expected to occur?

  • Second ionisation energy

  • First ionisation energy

  • Seventh ionisation energy

  • Sixth ionisation energy

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31 mark

The first ionisation energy of beryllium is higher than the first ionisation energy of boron. 

Which statement explains why?

  • Boron has a full outer shell

  • Boron has a larger atomic radius than beryllium

  • Beryllium has a more stable electronic configuration

  • The atomic number of beryllium is higher than boron

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41 mark

The electronic configurations of four different atoms are shown. 

Which atom has the highest first ionisation energy?

  • 1s2 2s2 2p6 3s2

  • 1s2 2s2 2p4

  • 1s2 2s2 2p6 

  • 1s2 2s2 

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51 mark

The table gives the successive ionisation energies for an element R.

 

1st

2nd

3rd

4th

5th

6th

Ionisation energy / kJ mol-1

950

1800

2700

4800

6000

12300

What could be the oxidation state of element R in its chloride?

  • +1

  • +2

  • +3

  • +4

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