A LevelChemistryCIETopic Questions1. Atomic Structure1.2 Isotopes

Syllabus Edition

First teaching 2023

First exams 2025

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Isotopes (CIE A Level Chemistry)

Topic Questions

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1a2 marks

Iron and cobalt are adjacent elements in the Periodic Table. Iron has three main naturally occurring isotopes, cobalt has one.

Explain the meaning of the term isotope.

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1b
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Isotopes of polonium, proton number 84, are produced by the radioactive decay of several elements including thorium, proton number 90. The isotope 213Po is produced from the thorium isotope 232Th.

Complete Table 1.1 below to show the atomic structures of the isotopes 213Po and 232Th.

Table 1.1 

Isotope Protons Neutrons  Electrons
213Po      
232Th      

 

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1c2 marks

Polonium has twenty five different isotopes.

Explain why the isotopes of polonium exhibit the same chemical reactions but their boiling points differ slightly.  

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2a2 marks

Atoms are made up of three subatomic particles; protons, neutrons and electrons. 

Table 2.1 below shows data about these particles.

Table 2.1

Particle

Proton

Neutron

Electron

Mass / kg

1.673 × 10-27

1.675 × 10-27

9.000 × 10-31

Calculate the mass of one atom of carbon in kg. Use data from Table 2.1 in your calculation. Show your working.

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2b2 marks

A sample of carbon contains 3 isotopes, 12C, 13C and 14C.

State one similarity and one difference in the properties of these isotopes of carbon. Explain your answer.

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2c
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A sample of element E contains five isotopes. The percentage abundance of the five isotopes is shown in Table 2.2. 

Table 2.2

isotope of E percentage abundance / %
46E 8.02
47E 7.31
48E 73.81
49E  
50E 5.32

i)
Calculate the percentage abundance of 49E.
 
[1]
 
ii)
Calculate the relative atomic mass, Ar, of element E to 1 decimal place. Use the data from Table 2.2 in your calculation.
 
[2]
 
iii)
Identify element E.
 
[1]

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3a1 mark

The symbols below describe two isotopes of the element antimony.

Sb presubscript 51 presuperscript 121      Sb presubscript 51 presuperscript 123

State the meaning of the term isotope.

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3b1 mark

State two ways in which these two isotopes of antimony are identical.

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3c1 mark

State the number of electrons present in one Sb2+ ion.

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