Edexcel A-Level Chemistry AS Paper 1, June 2019: Question 2

1 mark · Easy difficulty · Multiple Choice

Identify the electronic configuration of the sulfide ion, S2-.

Practise this question

Question

Multiple choice question 2 asking for the electronic configuration of the sulfide ion, S2-, with four options A, B, C, and D representing different electron configurations.
Question text

2 What is the electronic configuration of the sulfide ion, S2−?

A 1s22s22p63s23p2

B 1s22s22p63p4

C 1s22s22p63s23p4

D 1s22s22p63s23p6

(Total for Question 2 = 1 mark)

Mark scheme

Show the mark scheme Mark scheme for question 2 showing that the only correct answer is D, with explanatory notes detailing why options A, B, and C are incorrect.

How to answer it

Electronic Configuration of the Sulfide Ion (S²⁻)

What this question tests

This question assesses your understanding of atomic structure, specifically how to determine the electron configurations of negative ions (anions) by accounting for added electrons relative to the neutral atom, following standard subshell filling rules (aufbau principle).

Question 2: Electronic Configuration Analysis

Edexcel AS Level Chemistry

✅ Correct Answer: D

1s² 2s² 2p⁶ 3s² 3p⁶

Sulfur (S) has an atomic number of 16, meaning a neutral atom has 16 electrons. The sulfide ion (S²⁻) has gained 2 electrons, giving a total of 18 electrons. This fills the 3p subshell completely, achieving an isoelectronic configuration with argon.

💡 Key Knowledge

  • Neutral Sulfur: Atomic number 16 1s² 2s² 2p⁶ 3s² 3p⁴
  • Anion Formation: Negative ions gain electrons equal to their negative charge. S²⁻ adds 2 electrons.
  • Subshell Capacity: s-subshells hold max 2, p-subshells hold max 6 electrons.

🧠 Exam Technique

For multiple-choice questions involving ions, always count the total number of electrons first before looking at the options. Remember: Positive ions lose electrons; negative ions gain electrons.

❌ Common Errors & Distractor Analysis

  • Option C ( 1s² 2s² 2p⁶ 3s² 3p⁴ ): This is the configuration for a neutral sulfur atom, not the ion. A very common trap for rushing students!
  • Option A ( 1s² 2s² 2p⁶ 3s² 3p² ): This represents an incorrect electron count (14 electrons), which corresponds to an S²⁺ ion.
  • Option B ( 1s² 2s² 2p⁶ 3p⁴ ): This incorrectly removes electrons from the 3s subshell instead of maintaining proper subshell filling order.
Mark Allocation: 1 mark for selecting option D.

Topics

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

Question and mark scheme from the Edexcel A-Level Chemistry examination, AS Paper 1, June 2019. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.