Proposed that matter is composed of tiny particles called "atomos" (indivisible).
Thought properties of substances were due to the form of the atoms (e.g., iron atoms were hard).
Developments in Atomic Theory
Antoine Lavoisier:
Proposed the law of conservation of mass.
James Dalton:
Determined that elements exist as discrete packets of matter.
Investigation of Atomic Structure
Cathode Ray Experiments
Eugen Goldstein (1886):
Discovered positive rays emitted from the positive electrode in discharge tubes.
J.J. Thompson:
Investigated cathode rays and concluded they were negatively charged particles (electrons).
Developed the "plum pudding model" with electrons in a positive matrix.
Rutherford’s Gold Foil Experiment
Ernest Rutherford (1909):
Used alpha particles to discover that the positive charge is concentrated in a small area (nucleus).
Concluded most of the atom is empty space.
Discovered protons by bombarding nitrogen with alpha particles.
Bohr Model of the Atom
Niels Bohr (1911):
Applied mathematical models to predict electron positions.
Proposed the "planetary model" with electrons in orbits around a nucleus.
Quantum Theory
Werner Heisenberg:
Introduced the uncertainty principle: cannot know both momentum and position of an electron precisely.
Proposed the quantum theory where electrons are in probable regions called orbitals.
Modern Understanding
Quantum Model:
Electrons are found in orbitals, explained as cloud regions of probability.
Known orbitals: s, p, d, f forming sigma and pi bonds.
Conclusion
Atomic theory is built on centuries of scientific inquiry and remains an evolving field.
Each model has contributed to our understanding, but continuous questioning and experimentation are necessary.
Key Contributors
Script: Edi Gonzales
Editing: Blake de Pastino
Consultant: Dr. Heiko Langner
Direction & Filming: Nicholas Jenkins
Sound Design: Michael Aranda
Graphics: Thought Cafe
Important Takeaway
The study of chemistry and physics is essential to question and verify current models as science evolves. Continuing education and experimentation are crucial.