A Level Chemistry Revision "Electron Configuration and the Periodic Table"

Introduction

This tutorial provides a comprehensive overview of electron configuration and its relationship with the periodic table, specifically tailored for A Level Chemistry students. Understanding these concepts is essential for mastering chemistry topics and preparing for exams.

Step 1: Understand the Structure of the Periodic Table

• The periodic table is organized into blocks: s, p, d, and f.
• Each block corresponds to the type of electron sub-shell being filled.
• Familiarize yourself with the location of each block:
  • s-block: Groups 1 and 2
  • p-block: Groups 13 to 18
  • d-block: Transition metals (Groups 3 to 12)
  • f-block: Lanthanides and actinides

Step 2: Learn Electron Sub-shells and their Configurations

• Electron sub-shells are designated as s, p, d, and f, with varying capacities:
  • s can hold up to 2 electrons.
  • p can hold up to 6 electrons.
  • d can hold up to 10 electrons.
  • f can hold up to 14 electrons.
• The order of filling follows the Aufbau principle, which states that electrons occupy the lowest energy orbitals first.

Step 3: Practice Writing Electron Configurations

• Start with the atomic number of the element to determine the number of electrons.
• Follow the order of filling:
  1. Fill the 1s sub-shell first.
  2. Move to 2s, then 2p, 3s, 3p, 4s, 3d, 4p, and so on.
• Write the electron configuration using the sub-shells, for example:
  • For oxygen (atomic number 8): 1s² 2s² 2p⁴

Step 4: Verify Electron Configurations

• Use the periodic table to check if your electron configuration matches the element's position:
  • For elements in the same group, the outer electron configurations should be similar.
• Common pitfalls include miscounting electrons or incorrectly filling sub-shells.

Step 5: Understand Exceptions in Electron Configuration

• Some transition metals and heavier elements show anomalies in their electron configurations due to stability factors.
• Example: Chromium (Cr) and Copper (Cu) have configurations of:
  • Chromium: [Ar] 3d⁵ 4s¹
  • Copper: [Ar] 3d¹⁰ 4s¹
• Familiarize yourself with these exceptions for a deeper understanding.

Conclusion

Understanding electron configurations and the periodic table is crucial for A Level Chemistry. By following the structured steps outlined above, you can effectively write and verify electron configurations. Practice regularly and refer to the periodic table for clarity. As a next step, consider exploring specific elements and their configurations to solidify your knowledge further.