AQA A-Level Chemistry Paper 3, 2023: Question 19
1 mark · Medium difficulty · Multiple Choice
Trends in Period 3 Elements This question tests understanding of the periodic trends in Period 3 elements, including atomic radius, melting points, and first ionisation energies, and requires identifying an incorrect statement among the given options.
Practise this questionQuestion
Question text
19 Which statement is not correct about the Period 3 elements sodium to chlorine?
[1 mark]
A Sodium has the largest atomic radius.
B Sodium has the lowest melting point.
C Silicon has the highest melting point.
D Chlorine has the highest first ionisation energy.
Mark scheme
Show the mark scheme
19 B 1 (AO2) Sodium has the lowest melting point.
How to answer it
Understanding Period 3 Trends
Question
Which statement is not correct about the Period 3 elements sodium to chlorine?
- A: Sodium has the largest atomic radius.
- B: Sodium has the lowest melting point.
- C: Silicon has the highest melting point.
- D: Chlorine has the highest first ionisation energy.
Correct Answer: B
The correct answer is B: Sodium has the lowest melting point. This statement is not correct because chlorine, a molecular substance with weak van der Waals forces, has the lowest melting point among Period 3 elements.
- Metals like sodium have metallic bonding.
- Covalent network structures like silicon have very high melting points.
- Molecular substances like chlorine have low melting points due to weak intermolecular forces.
Explanation of Other Options
- A: Correct. Sodium has the largest atomic radius because atomic size decreases across a period due to increased nuclear charge.
- C: Correct. Silicon has the highest melting point due to its giant covalent structure with strong covalent bonds.
- D: Correct. Chlorine has the highest first ionisation energy because of its small atomic radius and high effective nuclear charge.
Summary of Key Period 3 Trends
- Atomic radius decreases across the period.
- Ionisation energy generally increases across the period.
- Melting points depend on structure and bonding:
- Metals: Sodium < Magnesium < Aluminium.
- Covalent network: Silicon has the highest melting point.
- Molecular: Phosphorus < Sulfur < Chlorine.
Final Answer
The correct answer is:
B: Sodium has the lowest melting point.
Topics
Inorganic Chemistry · 3.2.1 Periodicity
Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.