Cambridge IGCSE · Chemistry (0620)

Isotopes: Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Isotopes.

10 questions22 marksFree, no account

Question 1

1 mark

Which statement correctly defines isotopes of an element?

Question 2

1 mark

A sample of magnesium contains three isotopes:
\(^{24}Mg\) with an abundance of 79%
\(^{25}Mg\) with an abundance of 10%
\(^{26}Mg\) with an abundance of 11%
Calculate the relative atomic mass, \(A_r\), of magnesium in this sample to two decimal places.

Question 3

1 mark

Two particles, X and Y, have the same number of protons and the same number of electrons, but a different number of neutrons.
Which statement about X and Y is correct?

Question 4

1 mark

An atom of an element is represented by the symbol \( ^{27}_{13}Al \). What is the number of neutrons present in the nucleus of this atom?

Question 5

1 mark

The data below describes four different particles:

Particle 1: 17 protons, 18 neutrons, 17 electrons
Particle 2: 17 protons, 20 neutrons, 17 electrons
Particle 3: 18 protons, 18 neutrons, 18 electrons
Particle 4: 19 protons, 20 neutrons, 18 electrons

Which two particles are isotopes of the same element?

Question 6

2 marks

Define the term isotopes by referring to the subatomic particles found in the nucleus of an atom.

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Question 7

3 marks

An isotope of potassium is represented by the symbol \( ^{40}_{19}\text{K} \). State the number of neutrons in this isotope and explain why this isotope has a higher relative mass than the isotope \( ^{39}_{19}\text{K} \).

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Question 8

5 marks

Explain why the chemical properties of \( ^{35}\text{Cl} \) and \( ^{37}\text{Cl} \) are identical, whereas their physical properties, such as density, differ.

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Question 9

3 marks

a) Explain what is meant by the term isotopes.

b) An atom of element X has a proton number of 17 and a mass number of 35.

State the number of:

i) protons in an atom of X

ii) neutrons in an atom of X

iii) electrons in an atom of X

c) Another isotope of element X has a mass number of 37.

State the number of neutrons in this isotope.

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Question 10

4 marks

Chlorine exists as two naturally occurring isotopes: \(^{35}_{17}\text{Cl}\) and \(^{37}_{17}\text{Cl}\).
a) Define the term isotopes in terms of subatomic particles.
b) Explain why these isotopes have identical chemical properties.
c) Given that the relative atomic mass of chlorine is 35.5, calculate the percentage abundance of the \(^{35}\text{Cl}\) isotope. Show your working.

Write your answer out first, then check it against the worked solution.

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