Electron Configurations Lecture Notes

Introduction

• Objective: Learn how to find electron configurations for elements using the periodic table.

Steps to Find Electron Configurations

1. Determine Number of Electrons:

   • Use the periodic table to find the atomic number (number above the element symbol).
   • Atomic number indicates both the number of protons and electrons.

2. Periodic Table Layout:

   • Group 1 Elements: End in s1
   • Group 2 Elements: End in s2
   • P Block Elements:
     • Group 3 ends in p1, Group 4 ends in p2, up to Group 8 which ends in p6.
   • Transition Metals:
     • Start with d1 and go up to d10.

Examples

Boron

• Atomic Number: 5
• Configuration:
  • Period 1: 1s2 (Hydrogen)
  • Period 2:
    • 2s2 (Lithium and Beryllium)
    • 2p1 (Boron)
  • Result: 1s2 2s2 2p1

Chlorine

• Atomic Number: 17
• Configuration:
  • Period 1: 1s2
  • Period 2:
    • 2s2
    • 2p6
  • Period 3:
    • 3s2
    • 3p5 (Chlorine)
  • Result: 1s2 2s2 2p6 3s2 3p5

Vanadium

• Atomic Number: 23
• Configuration:
  • Period 1: 1s2
  • Period 2:
    • 2s2
    • 2p6
  • Period 3:
    • 3s2
    • 3p6
  • Period 4:
    • 4s2
    • D Block Adjustment: 3d3 instead of 4d3
  • Result: 1s2 2s2 2p6 3s2 3p6 4s2 3d3

Important Notes

• D Block Configuration: Subtract 1 from the period number when writing d block configurations.
• Practice: Key to mastering electron configurations is through consistent practice and checking your answers.

Conclusion: Understanding electron configurations involves familiarity with the periodic table order, recognizing element groups, and applying specific rules, especially for d block elements.**

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