The document traces the development of atomic theory over time from ancient Greek philosophers to modern models. It describes Democritus' idea that matter is made of indivisible particles called "atomos", Dalton's atomic theory of elements composed of atoms, J.J. Thomson's "plum pudding" model showing atoms contain smaller particles, Rutherford's gold foil experiment proving atoms have a small, dense nucleus, Bohr's model of electrons in specific energy levels orbiting the nucleus, and the modern wave model showing electrons as probability clouds rather than definite orbits.

2. Atomos: Not to Be Cut The History of Atomic Theory

5. Who are these men? In this lesson, we’ll learn about the men whose quests for knowledge about the fundamental nature of the universe helped define our views.

19. Thomson concluded that the negative charges came from within the atom. A particle smaller than an atom had to exist . The atom was divisible! Thomson called the negatively charged “ corpuscles, ” today known as electrons . Since the gas was known to be neutral, having no charge, he reasoned that there must be positively charged particles in the atom. But he could never find them.

29. Wave Model

34. X X X Wave X X X Bohr X X Rutherford X Thomson X Dalton X Greek Electron Cloud Orbit Nucleus Electron Indivisible