Lecture on Electrons and Atomic Structure

Introduction to Electrons

• Electrons are fundamental particles with:
  • Mass: 9.11 x 10^-31 kg
  • Charge: Negative
• Understanding electrons is key to understanding chemistry.
• Atoms change electron counts to achieve stability.

Electron Behavior and Bonds

• Atoms can:
  • Steal electrons creating ions (ionic bonds)
  • Share electrons (covalent bonds)
• Electrons are likely to be found in specific regions around the atom, known as electron orbitals.

Electron Spin and Orbitals

• Spin:
  • Property to describe angular momentum
  • Electrons can have "up" or "down" spin.
• Orbitals:
  • Maximum of two electrons per orbital with opposite spins due to Pauli Exclusion Principle.

Electron Shells and Subshells

• Orbitals grouped into shells based on energy.
• Shells labeled by principal quantum number (n).
  • Types of Orbitals:
    • s: Spherical, one per shell
    • p: Dumbbell-shaped, three per shell
    • d: Clover-shaped, five per shell
    • f: Unique shapes, seven per shell
• The number of orbitals per shell: n^2

Electron Configuration

• Electrons fill orbitals in specific sequence:
  • Aufbau Principle: Electrons fill from lower to higher energy.
  • Pauli Exclusion Principle: Max two electrons with opposite spins per orbital.
  • Hund’s Rule: Electrons spread out in orbitals of the same subshell to minimize repulsion.
• Configuration example:
  • Nitrogen (7 electrons): 1s² 2s² 2p³
• Ion formation changes electron configuration.

Noble Gas Configuration

• Used to simplify configurations for atoms with many electrons.
• Matches inner electron shells with a noble gas.
• Example: Phosphorus configuration starts with [Ne].

Filling Order Anomalies

• Some subshells fill in non-sequential order due to energy similarities.
• Examples:
  • 4s fills before 3d, but electrons are removed from 4s first.
  • Chromium and Copper have unique configurations due to stability.

Summary

• Electrons are central to chemical interactions.
• Different models (Bohr, probability clouds, configurations) help visualize their behavior and arrangement.
• Understanding electron arrangements aids in predicting chemical bonding and reactions.