M1-Lecture3_default

Overview of Atomic Theory

  • Atoms: Fundamental units of matter.

Early Models of Atomic Structure

  • Plum Pudding Model (1897): Proposed by J.J. Thompson. Atoms have electrons in a positive 'sea'; limitations in atomic structure.

  • Rutherford Model (1910): Alpha particles fired at gold foil; most passed through, some deflected. Concludes atoms contain a dense nucleus with protons and neutrons; electrons orbit like a solar system.

  • Bohr Model (1913): Electrons in fixed energy levels (orbitals); more organized view of electron arrangement.

  • Electron Cloud Model: Electrons in probabilistic orbitals, not fixed paths; higher probability near the nucleus.

Key Principles of Atomic Structure

  • Nucleus: Contains protons (positive) and neutrons (neutral).

  • Electrons: Negative charge in defined orbitals; each can hold 2 electrons with opposite spins.

Quantum Numbers and Orbitals

  • Principal Quantum Number (n): Energy levels (1, 2, 3).

  • Angular Momentum Quantum Number (l): Orbital shapes (s, p, d).

Electron Configuration

  • Fill orbitals in order of increasing energy (e.g., 1s, 2s, 2p).

  • Example: Carbon (6 electrons) → 1s² 2s² 2p²; follow Hund's rule for electron pairing.

Conclusion

  • Summary of atomic models and understanding of electron configuration and probabilities.