Interactive visuals for atomic structure: subatomic particles, Thomson's model, Rutherford scattering, Bohr orbits, and hydrogen spectral lines.
Atoms are built from protons, neutrons, and electrons. The animation separates them as the three basic particles discussed in the chapter.
This model treats the atom as a diffuse positively charged sphere with electrons embedded inside it, like plums in a pudding.
Useful contrast: Thomson had no compact nucleus in this model.
Most alpha particles pass straight through gold foil, some deflect, and a very few rebound. That implies a tiny, dense, positively charged nucleus.
Electrons move in allowed circular orbits. When an electron jumps from a higher orbit to a lower one, energy is emitted as radiation.
Memory point: energy is absorbed or emitted only during transition between allowed orbits.
Hydrogen shows a line spectrum. Different electronic transitions produce lines in different regions, including visible Balmer lines.
Exam cue: Lyman is ultraviolet, Balmer is visible, and Paschen/Brackett/Pfund are infrared.