IGCSE Chemistry 0620
Past Paper Practice: Topic 2.3 - Isotopes
Cambridge Examination Style | Papers 2 & 4
📋 Examination Instructions
- • Answer all questions
- • Show all working where applicable
- • Use the Periodic Table provided (see syllabus)
- • Total marks: 30 marks
- • Recommended time: 35 minutes
Section A: Definitions & Core Concepts
Questions 1-5 | 10 marks
Question 1
Define the term isotope.
[2 marks]
Question 2
Complete the table below for the isotopes of chlorine.
| Isotope Symbol | Proton Number | Nucleon Number | Number of Neutrons |
|---|---|---|---|
| 3517Cl | _____ | _____ | _____ |
| 3717Cl | _____ | _____ | _____ |
[2 marks]
Question 3
Write the symbol for the isotope of carbon that has:
- (a) 6 protons and 6 neutrons
- (b) 6 protons and 8 neutrons
[2 marks]
Question 4
State two types of isotopes.
[2 marks]
Question 5
Give one example each of:
- (a) A medical use of radioactive isotopes
- (b) An industrial use of radioactive isotopes
[2 marks]
Section B: Atomic Structure Calculations
Questions 6-10 | 10 marks
Question 6
Uranium-235 is used as nuclear fuel. The proton number of uranium is 92.
Calculate the number of neutrons in one atom of uranium-235.
[2 marks]
Question 7
An atom of element X has 19 protons and 20 neutrons.
- (a) State the proton number of element X. [1]
- (b) State the nucleon number of element X. [1]
[2 marks]
Question 8
Magnesium has three naturally occurring isotopes:
24Mg, 25Mg, and 26Mg
How many neutrons are present in each isotope?
[2 marks]
Question 9
The table shows information about two atoms.
| Atom | Proton Number | Nucleon Number |
|---|---|---|
| A | 8 | 16 |
| B | 8 | 18 |
Are atoms A and B isotopes of the same element? Explain your answer.
[2 marks]
Question 10
Complete the symbol for the chloride ion by adding the nucleon number and the charge.
___17Cl___
The chloride ion has 18 neutrons and 18 electrons.
[2 marks]
Section C: Chemical Properties (Supplement)
Questions 11-15 | 10 marks
Question 11
Explain why 35Cl and 37Cl have the same chemical properties.
[2 marks]
Question 12
Carbon-12 and carbon-14 are isotopes of carbon.
State one similarity and one difference in the chemical properties of these two isotopes.
[2 marks]
Question 13
Hydrogen has three isotopes: 1H, 2H (deuterium), and 3H (tritium).
- (a) Write the electronic configuration of all three isotopes. [1]
- (b) Explain why all three isotopes react with oxygen in the same way. [2]
[3 marks]
Question 14
Copper has two main isotopes: 63Cu (69% abundance) and 65Cu (31% abundance).
Calculate the relative atomic mass (Ar) of copper.
[2 marks]
Question 15
A student makes the following statement:
"Isotopes of the same element have different chemical properties because they have different masses."
Is this statement correct? Explain your answer fully.
[3 marks]
🎯 Key Exam Success Tips
✓ Definition Keywords
- • "Same element" = same proton number
- • "Different neutrons" = different mass
- • Always use "nucleon number" OR "mass number"
🚨 Common Traps
- • Confusing proton number with mass number
- • Saying "mass" affects chemical properties
- • Forgetting that ELECTRONS control chemistry
📐 Formula Mastery
- • Neutrons = Mass number - Proton number
- • Charge = Protons - Electrons
- • Ar = Σ(mass × abundance) / 100
💡 Memory Tricks
- • "I-SO-TOPE": Same element, different mass
- • Chemical = Electrons (outer shell)
- • Physical = Neutrons (mass difference)
🎓 END OF EXAMINATION
Total: 30 marks | Check your answers carefully!
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