Summary of Atomic Theory Lecture

Introduction to Atomic Theory

• Visualization of atoms today involves complex models.
• Early atomic theory began with Greek philosophers Leucippus and Democritus.
  • Concept: Matter is composed of indivisible particles, "a-tomos".
  • Atoms attributed with properties of substances (e.g., hardness of iron).

Evolution of Atomic Theory

• Antoine Lavoisier (Late 1700s)
  • Law of Conservation of Mass: Mass remains constant despite changes in form.
• James Dalton (Early 1800s)
  • Elements described as discrete packets of matter.

Investigating Atomic Structure

• 1870s: Use of discharge tubes to explore atomic composition.
  • Cathode rays discovered to have a negative charge.
  • Eugen Goldstein noted positive charges (anode rays).

Advanced Discoveries

• J.J. Thomson (1897)
  • Identified electrons (originally "corpuscles") as negatively charged particles.
  • Proposed the "plum pudding model".
    • Electrons scattered within a positively charged "matrix".

Rutherford's Contributions

• Ernest Rutherford (1909)
  • Gold foil experiment revealed the nucleus through deflection of alpha particles.
  • Concluded atoms are mostly empty space with a dense, positive nucleus.
  • Identified protons as fundamental particles.

Bohr and the Planetary Model

• Niels Bohr (1911)
  • Integrated Rutherford’s findings with electromagnetic theory.
  • Suggested electrons orbit the nucleus, forming a "planetary model".

Heisenberg and Quantum Theory

• Werner Heisenberg (1920s)
  • Uncertainty Principle: Position and momentum of electrons can’t be precisely known simultaneously.
  • Introduced quantum theory: Electrons exist within probability orbitals (s, p, d, f).
  • Developed the "cloud model" of atomic structure.

Conclusion

• Atomic theory evolved through contributions of many scientists, from early philosophical ideas to modern quantum theory.
• Acknowledgment of potential for further discoveries and changes to current models.
• Importance of continued questioning and experimentation in chemistry and physics.

Credits

• Written by Edie Gonzalez, Edited by Blake de Pastino
• Chemistry consultant: Dr. Heiko Langner
• Production: Nicholas Jenkins, Katherine Green, Michael Aranda, Thought Cafe Graphics Team