CAIE A-Level Chemistry 1.2 Isotopes

Practise defining isotopes and linking neutron-number differences to physical properties, abundance and relative atomic mass.

Exam points

define isotopes as atoms of the same element with equal proton number but different neutron numbers
explain identical chemical properties through the same electron configuration
use isotopic mass and percentage abundance to calculate or interpret relative atomic mass

Covered syllabus points

1.2.1—Terms: isotope 1.2.2—The notation x 1.2.3—Isotopes of the same element have the same 1.2.4—Isotopes of the same element have different

[Maximum number: 3]

The model of the nuclear atom was first proposed by Ernest Rutherford. He developed this model on the basis of results obtained from an experiment using gold metal foil.

(a)

A sample of gold found in the earth consists of only one isotope.

[ 3 ]

(i)

Explain what is meant by the term isotopes.

[ 2 ]

(ii)

A different sample of gold contains more than one isotope.

Suggest why this different sample of gold has the same chemical properties as the sample found in the earth.

[ 1 ]

[Maximum number: 3]

An isotope of copper has a relative isotopic mass of 65 .

Complete Table 1.2 for an atom of copper-65.

Table 1.2

Correct completed table:

isotope	atomic number	nucleon number	number of neutrons	electronic arrangement
copper-65	29	65	65-29=36	$1\mathrm{s}^{2}2\mathrm{s}^{2}2\mathrm{p}^{6}3\mathrm{s}^{2}3\mathrm{p}^{6}3\mathrm{d}^{10}4\mathrm{s}^{1}$

M1: 29 and 65.
M2: nucleon number - atomic number; allow ECF from M1.
M3: electronic arrangement.

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Covered syllabus points

1.2 Isotopes question 1

Question (a)

Question (i)

Question (ii)

1.2 Isotopes question 2