AQA A-Level Chemistry AS Paper 1, November 2021: Question 12

1 mark · Medium difficulty · Multiple Choice

Identify the electron configuration of V2+ in the ground state

Practise this question

Question

Multiple choice question numbered 1 2 asking for the electron configuration of V2+ in the ground state, worth 1 mark. Four options are provided: A (1s2 2s2 2p6 3s2 3p6 3d3), B (1s2 2s2 2p6 3s2 3p6 3d1 4s2), C (1s2 2s2 2p6 3s2 3p6 3d3 4s2), and D (1s2 2s2 2p6 3s2 3p6 3d5 4s2).
Question text

12 What is the electron configuration of V2+ in the ground state?

[1 mark]

A 1s2 2s2 2p6 3s2 3p6 3d3

B 1s2 2s2 2p6 3s2 3p6 3d1 4s2

C 1s2 2s2 2p6 3s2 3p6 3d3 4s2

D 1s2 2s2 2p6 3s2 3p6 3d5 4s2

Mark scheme

Show the mark scheme Mark scheme indicating question number 12, correct answer A, awarding 1 mark for the electron configuration 1s2 2s2 2p6 3s2 3p6 3d3.

12 A 1 1s2 2s2 2p6 3s2 3p6 3d3

How to answer it

Electron Configuration of Transition Metal Ions (V²⁺)

What this question tests

This question assesses your ability to determine the ground-state electron configuration of transition metal ions. Specifically, it tests your knowledge of the fill order of atomic orbitals (the 4s filling before 3d rule) and crucially, the removal order of electrons when transition metal ions form positive ions (electrons are always lost from the 4s orbital before the 3d orbital).

Question 1.2

Determine the ground-state electron configuration of V²⁺

✅ Correct Answer: A

1s² 2s² 2p⁶ 3s² 3p⁶ 3d³

Mark Awarded: 1 / 1 for selecting option A.

💡 Key Knowledge

  • Vanadium (V) has atomic number Z = 23 .
  • Neutral V atom configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s² .
  • When forming transition metal ions, electrons are lost from the 4s orbital first, not the 3d orbital, due to energy level changes upon filling.
  • Removing 2 electrons from neutral vanadium means removing the two 4s electrons, leaving 3d³ .

🧠 Exam Technique

  • Always write out the neutral atom configuration first if you are unsure.
  • Cross out electrons starting from the highest principal quantum shell number (n=4 before n=3).
  • Double-check subshell ordering: note that 3d is written before 4s when empty/partially filled in standard ionic configurations, or simply ensure you subtracted from the right place.

❌ Common Errors

  • Distractor C ( 3d³ 4s² ): This is the configuration for a neutral vanadium atom, not the V²⁺ ion. Students frequently forget to remove electrons when they see a positive charge.
  • Distractor B ( 3d¹ 4s² ): Students mistakenly remove electrons from the 3d subshell instead of the 4s subshell, showing a fundamental misunderstanding of transition metal ionization.

Topics

Physical Chemistry · 3.1.1 Atomic Structure

Question and mark scheme from the AQA A-Level Chemistry examination, AS Paper 1, November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.