OCR A-Level Chemistry AS Breadth in chemistry (01), June 2018: Question 8

1 mark · Easy difficulty · Multiple Choice

Identify the property that determines the order of elements in the Periodic Table.

Practise this question

Question

Multiple choice question 8 asking what determines the order of elements in the Periodic Table, with four options: A first ionisation energy, B number of electrons in the outer shell, C number of protons in the nucleus, and D relative atomic mass. Below is an answer box and the mark allocation of [1].
Question text

8 What determines the order of elements in the Periodic Table?

A first ionisation energy

B number of electrons in the outer shell

C number of protons in the nucleus

D relative atomic mass

Your answer [1]

Mark scheme

Show the mark scheme Mark scheme for question 8 showing the correct answer as C, worth 1 mark.

8 C 1

How to answer it

Determining the Order of Elements in the Periodic Table

OCR AS Level Chemistry • Multiple Choice Question

What this question tests

This question assesses your foundational historical and structural knowledge of the Periodic Table. Specifically, it tests whether you know the fundamental property that distinguishes one element from another and dictates their sequential arrangement (atomic number / proton number versus relative atomic mass).

Question 8: Multiple Choice

Determining Periodic Order

✅ Correct Answer: C

number of protons in the nucleus (Atomic Number, Z)

Elements in the modern Periodic Table are arranged strictly in order of increasing atomic number (number of protons).

💡 Key Knowledge

  • Mendeleev's table was originally ordered by relative atomic mass, which led to anomalies (e.g., iodine and tellurium).
  • Henry Moseley later discovered atomic numbers using X-ray spectra, proving that the nuclear charge defines the element.
  • Proton number uniquely identifies an element and remains constant across isotopes.

🧠 Exam Technique

Read all options carefully before committing. Do not confuse historical development (relative atomic mass) with the modern definition (proton number).

❌ Common Errors

Many students incorrectly choose D (relative atomic mass) because they associate early periodic tables with atomic weights, forgetting that the modern periodic table corrects these anomalies using proton numbers.

Mark Allocation: 1 mark available for selecting C.

Topics

Module 2: Foundations in chemistry · Module 3: Periodic table and energy · 2.1 Atoms and reactions · 3.1 The periodic table

Question and mark scheme from the OCR A-Level Chemistry examination, AS Breadth in chemistry (01), June 2018. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.