A LevelChemistryCIETopic Questions1. Atomic Structure1.1 Particles in the Atom & Atomic Radius

Syllabus Edition

First teaching 2023

First exams 2025

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Particles in the Atom & Atomic Radius (CIE A Level Chemistry)

Topic Questions

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11 mark

The reaction shown occurs in gas clouds throughout the Universe.

H2 (g) + H2+ (g) → H (g) + H3+ (g)

What is the atomic structure of the H3+ ion?

 

protons

neutrons

electrons

A

B

C

D

3

3

2

2

0

0

1

1

1

2

1

2

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21 mark

Which row is correct?

 

the atomic number is the number of

the proton number is the number of

the mass number is the number of

A

B

C

D

atoms

electrons

electrons

protons

protons

neutrons

neutrons

protons

protons

nucleons

protons

nucleons

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31 mark

The phosphide ion, begin mathsize 16px style P presubscript 15 presuperscript 32 superscript 3 minus sign end superscript end style, is used in medicine as a radioactive treatment for some forms of cancer. 

What is the composition of the phosphide ion?

 

protons

neutrons

electrons

A

B

C

D

15

15

17

17

17

17

15

15

32

18

15

32

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41 mark

Which option correctly describes the relative charges and masses of the subatomic particles?

 

proton

neutron

electron

the relative mass of an electron

A

B

C

D

+1

0

+1

0

0

+1

0

+1

-1

+1

-1

-1

1

begin mathsize 14px style 1 over 1840 end style

1 over 1840

1

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51 mark

Which row correctly describes the characteristics of the nucleus and surrounding space?

 

Nucleus

Surrounding space

A

B

C

D

Small, dense and neutral

Large, dense and positive

Large, dense and neutral

Small, dense and positive

Mainly empty space

Densely populated with electrons

Densely populated with electrons

Mainly empty space

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61 mark

X is a particle with 19 electrons and 20 neutrons. 

Which of the species is X?

  • 40Ca+

  • 39K+

  • 38Ar

  • 45Sc

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11 mark

The species Cl-, K+ and Ar are isoelectronic. This means that they have the same number of electrons. 

In which order do their radii decrease?

 

Largest   →   Smallest

A

B

C

D

K+

Cl-

K+

Ar

Cl-

Ar

Ar

K+

Ar

K+

Cl-

Cl-

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21 mark

The trajectories of subatomic particles shot through an electric field produced in a vacuum are shown in the diagram. 

1-1-q22-subatomic-particles-in-electric-field-2

Which statements is incorrect?

  • The proton and electron are deflected because they are charged particles.

  •  The neutrons are undeflected as they have no charge.

  • The electron is deflected more than the proton because it has less mass.

  • The particles travel at different speeds

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31 mark

Which of the following statements about the trend in atomic radius across Period 3 is incorrect?

  • Electrons shells are added moving across the period which increases the nuclear force of attraction

  • The nuclear charge increases moving across due to increasing atomic number

  • There is a greater force of attraction between the nucleus and the electrons

  • The atomic radius decreases across the period 

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41 mark

What is the total number of protons and electrons in two moles of hydrogen gas?

  • 4

  • 8

  • 2.4 x 1024

  • 4.8 x 1024

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11 mark

In which of the following species are the numbers of protons, neutrons and electrons all different?

  • 23Na+

  • 27Al

  • 19F-

  •  32S2-

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21 mark

The atomic number of an element gives the number of protons in the nucleus which is also equal to the number of electrons. Which statement explains why atoms are neutral?

  • One proton has a mass 1840 times greater than one electron.

  • The charge on an electron is equal and opposite to the charge on a proton.

  • The difference in charge between electrons and protons is balanced by the neutrons.

  • Electrons are spread out in shells around the nucleus while protons are concentrated inside the nucleus.

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31 mark

Which statement about atomic radius in Group I elements Na to Rb is incorrect?

  • Increases moving down the group

  • Increases moving down due to the addition of electron shells 

  • Decreases moving down due to increasing nuclear forces

  • Rb has the greatest atomic radius

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4
Sme Calculator1 mark

Which is the correct number of subatomic particles for a phosphide ion?

  Protons Neutrons Electrons
A 15 16 18
B 16 15 16
C 16 15 18
D 15 15 15

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51 mark

Which row correctly describes the subatomic particles found in 26Mg2+?

             

     protons        

     neutrons      

     electrons       

A

10

14

12

B

12

14

10

C

12

26

10

D

14

12

12

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