OCR A-Level Chemistry Periodic table, elements and physical chemistry (01), June 2019: Question 14

1 mark · Medium difficulty · Multiple Choice

Identify the correct properties of a transition element from a given list of statements about partially filled d sub-shells, variable oxidation states, and coloured ions.

Practise this question

Question

Multiple choice question 14 asking which properties are correct for a transition element: 1. The element has atoms with a partially filled d sub-shell, 2. The existence of more than one oxidation state in its compounds, 3. The formation of coloured ions. Four options A, B, C, D are provided with a box for the answer.
Question text

14 Which property/properties is/are correct for a transition element?

1 The element has atoms with a partially filled d sub-shell.

2 The existence of more than one oxidation state in its compounds.

3 The formation of coloured ions.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer [1]

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer for question 14 is C, worth 1 mark.

14 C 1 AO1.1

How to answer it

Transition Element Properties

What this question tests

This question assesses your precise definition-level knowledge of transition elements, specifically differentiating between the electronic configuration requirements of transition metals (having an ion with a partially filled d sub-shell) versus general d-block elements, alongside their chemical characteristics like variable oxidation states and coloured ion formation.

Question 14

Exam Breakdown & Correct Answer

✅ Correct Answer: C (Only 2 and 3)

The correct option is C. Statements 2 and 3 are correct properties of transition elements, while statement 1 contains a subtle but crucial technical error regarding atoms vs. ions.

💡 Key Knowledge

  • Definition: A transition element is a d-block element that forms an ion with a partially filled d sub-shell.
  • Scandium & Zinc trap: Sc forms only Sc³⁺ (empty d-sub-shell) and Zn forms only Zn²⁺ (full d-sub-shell). Neither is a transition element!
  • Variable Oxidation States: Caused by small energy differences between 4s and 3d orbitals.
  • Coloured Ions: Due to d-d electron transitions when visible light hits split d-orbitals.

🧠 Exam Technique

Read every word carefully! Multiple-choice questions testing definitions often use the words 'atoms' instead of 'ions' to trap students who memorize phrases loosely without understanding the underlying chemistry.

❌ Common Errors

  • Statement 1 trap: Selecting options containing statement 1. Neutral atoms of copper have a 3d¹⁰ 4s¹ configuration (completely filled d sub-shell in the atom, though Cu²⁺ has 3d⁹ ). More importantly, the formal IUPAC definition specifies an ion with a partially filled d sub-shell, not an atom.
Mark Scheme Note: 1 mark awarded for selecting C (AO1.1 Knowledge and Understanding).

Topics

Module 5: Physical chemistry and transition elements · 5.3 Transition elements

Question and mark scheme from the OCR A-Level Chemistry examination, Periodic table, elements and physical chemistry (01), June 2019. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.