20: Modern Physics Last updated Save as PDF Page ID581 Contributed by CK12CK12 20.1: Fundamental Particles20.2: Atomic Forces20.3: Bohr's Atomic Model20.4: Quantum Mechanical Atomic Model20.5: Quarks20.6: Isotopes and Nuclear Stability20.7: Radioactivity20.8: Nuclear Reactions20.9: Nuclear Reactors20.10: Special Theory of Relativity20.11: General Theory of Relativity