Quantum Mechanical Model of Atoms: Electron Configuration

Introduction

Presenter: Iman Platform: YouTube Series: High Yield MCAT General Chemistry Video: #7 Topic: Electron Configuration (Part Two)

Key Concepts

Electron Configuration

• Definition: Distribution of an atom's electrons among various orbitals.
• Basis: Quantum mechanical principles.
• Importance: Explains arrangement of electrons within an atom.

Principles Governing Electron Configuration

1. Aufbau Principle:

   • Electrons fill orbitals starting from the lowest energy level to higher energy levels.
   • Example: 1s orbital fills before 2s orbital.
   • Visual representation: Periodic table order of elements.

2. Pauli Exclusion Principle:

   • Each orbital can hold a maximum of 2 electrons with opposite spins.
   • No two electrons can have the same set of all four quantum numbers.

3. Hund’s Rule:

   • Electrons fill degenerate (equal energy) orbitals first before pairing up.
   • Minimizes electron-electron repulsion and is energetically favorable.

Writing Electron Configurations

• Critical Skill: Helpful for chemists and MCAT preparation.
• Energy Levels: Increase generally with the principal quantum number (n).
  • Example: 3d orbitals have higher energy than 4s orbitals despite '4' being a larger number than '3'.
• Simplified Order: Can be derived from the periodic table.
  • S, D, P, and F orbitals are read based on periodic table locations.

Example: Carbon (C)

• Position: Identify Carbon's location on the periodic table.
• **Configuration Steps: **
  1. 1s2: Fill the 1s orbital.
  2. 2s2: Fill the 2s orbital.
  3. 2p2: Move to the 2p orbital and fill 2 boxes.
• Result: Electron configuration for Carbon = 1s2 2s2 2p2.

Conclusion

• Review: Periodic table as a tool for electron configurations.
• Practice: Writing configurations for different elements.
• Encouragement: Good luck, happy studying, and best wishes to future doctors!

Questions and Comments Welcome!