AQA A-Level Chemistry Paper 3, 2021: Question 22

1 mark · Easy difficulty · Multiple Choice

This question tests your understanding of the structure and bonding in different substances. It asks you to identify which substance contains delocalised electrons — electrons that are not associated with a single atom or bond but are free to move across a structure. These delocalised electrons are responsible for properties such as electrical conductivity in certain materials.

Practise this question

Question

AQA A-Level Chemistry Paper 3, 2021: Question 22
Question text

22 Which substance contains delocalised electrons?

[1 mark]

A cyclohexane

B graphite

C iodine

D sodium chloride

Mark scheme

Show the mark scheme Mark scheme for AQA A-Level Chemistry Paper 3, 2021: Question 22

22 B 1 graphite

How to answer it

Multiple Choice Explained: Which substance contains delocalised electrons?

Correct Answer: B – Graphite

Why? In graphite, each carbon atom forms three covalent bonds, leaving one electron per carbon atom delocalised. These delocalised electrons are free to move and conduct electricity along the layers of graphite.

Why A is incorrect:

Cyclohexane is a saturated hydrocarbon (an alkane). All the electrons are involved in sigma (σ) bonds – no delocalisation occurs in its bonding.

Why C is incorrect:

Iodine consists of I2 molecules held together by van der Waals forces in a simple molecular lattice. There are no delocalised electrons.

Why D is incorrect:

Sodium chloride is an ionic lattice made of Na+ and Cl− ions. All electrons are localised within the ions, so it does not contain any delocalised electrons.

Topics

Physical Chemistry · 3.1.3 Bonding

Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.