Isotopes (Cambridge (CIE) O Level Chemistry): Exam Questions

Protons, neutrons and electrons are subatomic particles.

Complete the table to show the relative mass and relative charge of a proton, a neutron and an electron.

Bromine has two isotopes.

Define the term isotope.

Explain why the two isotopes of bromine have the same chemical properties.

The table shows the number of protons, neutrons and electrons in some atoms and ions.

Complete the table.

This question is about elements X, Y and Z.

An atom of element X is represented as ${}_{16}{}^{34}\mathrm{X}$

Name the different types of particles found in the nucleus of this atom of X.

What is the term for the total number of particles in the nucleus of an atom?

What is the total number of particles in the nucleus of an atom of ${}_{16}{}^{34}\mathrm{X}$ ?

What is the electronic structure of the ion X^2–?

What term is used to describe atoms of the same element with different numbers of particles in the nucleus?

Part of the definition of relative atomic mass is ‘the average mass of naturally occurring atoms of an element’.

Some relative atomic masses are not whole numbers.

Element Y has only two different types of atom, ⁶⁹Y and ⁷¹Y

The ratio of atoms present in element Y is shown.

⁶⁹Y : ⁷¹Y = 3 : 2

• Calculate the relative atomic mass of element Y to one decimal place.

• Identify element Y.

Element Z is in Period 3 and Group V.

Explain in terms of electron transfer why Z behaves chemically as a non-metal.

Chlorine is in Group VII of the Periodic Table.

Two isotopes of chlorine are chlorine‑35 and chlorine‑37

State why these two isotopes of chlorine have the same chemical properties.

Chlorine is in Group VII of the Periodic Table.

Two isotopes of chlorine are chlorine‑35 and chlorine‑37.

Complete the table to show the number of electrons, neutrons and protons in each atom and ion.

${}_{11}{}^{22}\mathrm{Na}$, ${}_{11}{}^{23}\mathrm{Na}$ and ${}_{11}{}^{24}\mathrm{Na}$ are isotopes of sodium.

Describe how these sodium isotopes are the same and how they are different in terms of the total number of protons, neutrons and electrons in each.

same:

different:

${}_{11}{}^{22}\mathrm{Na}$, ${}_{11}{}^{23}\mathrm{Na}$ and  ${}_{11}{}^{24}\mathrm{Na}$ are isotopes of sodium.

Why do all three isotopes have an overall charge of zero?

This question is about the structures of atoms and ions.

Define the term proton number.

Complete the table to show the number of protons, neutrons and electrons present in atoms of ${}_{12}{}^{24}\mathrm{Mg}$ and ${}_{12}{}^{26}\mathrm{Mg}$.

What term is used to describe atoms of the same element, such as ${}_{12}{}^{24}\mathrm{Mg}$ and ${}_{12}{}^{26}\mathrm{Mg}$?

Explain why the chemical properties of ${}_{12}{}^{24}Mg$ and ${}_{12}{}^{26}Mg$ are the same.

Complete the table to identify the atoms and ions which have the following numbers of protons, neutrons and electrons.

State the electronic structure of the following atom and ion.

Al:

S^2–:

The symbols of three particles are shown.

${}_{82}{}^{206}\text{Pb}$

${}_{82}{}^{208}\text{Pb}$

Give the number of neutrons in an atom of ${}_{82}{}^{208}\text{Pb}$

The symbols of three particles are shown.

${}_{82}{}^{206}\text{Pb}$

${}_{82}{}^{208}\text{Pb}$

Explain why ${}_{82}{}^{206}\text{Pb}$ and ${}_{82}{}^{208}\text{Pb}$ are isotopes of each other.

The symbols of three particles are shown.

${}_{82}{}^{206}\text{Pb}$

${}_{82}{}^{208}\text{Pb}$

The ion has the same number of protons and the same number of neutrons as the atom ${}_{82}{}^{206}\text{Pb}$

Explain why is not an isotope of ${}_{82}{}^{206}\text{Pb}$

Element Q has two isotopes, ⁸⁵Q and ⁸⁷Q.

The relative atomic mass of Q is 85.5

Calculate the percentage abundance of each isotope in a sample of Q.

A second sample of Q is found in which the proportion of ⁸⁷Q is higher.

State the effect of this on the relative atomic mass of Q.

Explain your answer.

Element G has two isotopes. One isotope has a nucleon number of x and the other has a nucleon number of x + 4.

In a sample of G, the two isotopes are present in the ratio 2 : 3, with the lighter isotope first.

Show that the relative atomic mass of G is x + 2.4

The relative atomic mass of G is 30.4

Deduce the nucleon number of each isotope of G.

Element W has three isotopes, ⁵⁴W, ⁵⁶W and ⁵⁷W.

In a sample of W, 90.0% of the atoms are ⁵⁶W.

Of the remaining atoms, there are 4 times as many ⁵⁴W atoms as ⁵⁷W atoms.

Deduce the percentage abundance of ⁵⁴W and of ⁵⁷W.

Calculate the relative atomic mass of W.

Give your answer to one decimal place.

Element L has three isotopes, ²⁰L, ²²L and ²⁴L.

In a sample of L, 90.0% of the atoms are ²⁰L and the relative atomic mass of L is 20.3

Calculate the percentage abundance of ²²L and of ²⁴L in this sample.

A second sample of L also contains 90.0% ²⁰L, but this sample has a relative atomic mass of 20.2

Deduce the percentage abundance of each isotope in this second sample.

The table shows the proton numbers and the accurate relative atomic masses of three neighbouring elements.

Suggest why tellurium has a higher relative atomic mass than iodine.

The table shows the proton numbers and the accurate relative atomic masses of three neighbouring elements.

State and explain whether the relative atomic mass of an element always increases as its proton number increases.