Edexcel A-Level Chemistry AS Paper 1, June 2024: Question 3

1 mark · Easy difficulty · Multiple Choice

Identify the correct trend in atomic radii across Period 2 and down Group 2.

Practise this question

Question

Multiple choice question 3 asking which pair of responses shows the trend in atomic radii of atoms, excluding the noble gases (Group 0). A table provides four options labeled A to D, showing combinations of increasing or decreasing for the trend across Period 2 and the trend down Group 2.
Question text

3 Which pair of responses show the trend in atomic radii of atoms, excluding the

noble gases (Group 0)?

Trend across Period 2 Trend down Group 2

A increasing increasing

B increasing decreasing

C decreasing decreasing

D decreasing increasing

(Total for Question 3 = 1 mark)

Mark scheme

Show the mark scheme Mark scheme indicating that the only correct answer is D, with brief explanations for why options A, B, and C are incorrect.

Question

Answer Mark

Number

3 The only correct answer is D (decreasing, increasing) (1)

A is incorrect because atomic radii decrease across Period 2

B is incorrect because atomic radii decrease across Period 2 and increase down Group 2

C is incorrect because atomic radii increase down Group 2

(Total for Question 3 = 1 mark)

How to answer it

Trends in Atomic Radii

📋 What this question tests

This question assesses your core understanding of periodic trends across the Periodic Table. Specifically, it tests your knowledge of how atomic radius changes across a period (specifically Period 2) and down a group (specifically Group 2), and the underlying atomic structure reasons for these changes.

Question 3 (Multiple Choice)

Trend in atomic radii across Period 2 and down Group 2

✅ Correct Answer

D (decreasing, increasing)

Worth 1 mark. No partial credit for multiple-choice questions.

💡 Key Knowledge

  • Across a period (Period 2): Atomic radius decreases because nuclear charge increases while shielding remains roughly constant, pulling electrons closer.
  • Down a group (Group 2): Atomic radius increases because extra main electron shells are added, increasing shielding and distance from the nucleus.

🧠 Exam Technique

Tackle multiple-choice questions systematically. Evaluate one trend at a time to quickly eliminate incorrect options. For example, knowing that atomic radius decreases across Period 2 immediately eliminates options A and B.

❌ Common Errors

  • Option A: States atomic radius increases across Period 2 (forgetting that increased nuclear charge pulls the electron cloud tighter).
  • Option B & C: Incorrectly state that atomic radius decreases down a group, confusing atomic radius trends with ionisation energy or electronegativity trends.

Topics

Physical Chemistry · Inorganic Chemistry · Topic 1: Atomic Structure and the Periodic Table · Topic 4: Inorganic Chemistry and the Periodic Table

Question and mark scheme from the Edexcel A-Level Chemistry examination, AS Paper 1, June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.