Discovery of the atom By Delmark42@gmail.com 1803 The Solid Sphere Model was the first atomic model and was developed by John Dalton in the early 19th century. https://thehistoryoftheatomicmodel.weebly.com/the-solid-sphere-model.html#:~:text=The%20Solid%20Sphere%20Model%20was,of%20his%20research%20into%20gases. Period: 1803 to May 15, 2021 Discovery of the atom 1904 Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons https://www.khanacademy.org/science/ap-chemistry/electronic-structure-of-atoms-ap/history-of-atomic-structure-ap/a/discovery-of-the-electron-and-nucleus#:~:text=Thomson's%20experiments%20with%20cathode%20ray,positively%2Dcharged%20%22soup.%22 1911 Rutherford model description of the structure of atoms proposed (1911) by the New Zealand-born physicist Ernest Rutherford https://www.britannica.com/science/Rutherford-model 1913 According to the Bohr model, often referred to as a planetary model, the electrons encircle the nucleus of the atom in specific allowable paths called orbits. https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Book%3A_Introductory_Chemistry_(CK-12)/05%3A_Electrons_in_Atoms/5.06%3A_Bohr's_Atomic_Model#:~:text=According%20to%20the%20Bohr%20model,orbits%2C%20its%20energy%20is%20fixed. 1926 Erwin Schrödinger proposed the quantum mechanical model of the atom, which treats electrons as matter waves. https://www.khanacademy.org/science/physics/quantum-physics/quantum-numbers-and-orbitals/a/the-quantum-mechanical-model-of-the-atom May 15, 2021 Today's Date