Pioneers of Atomic Theory and Structure
Researcher | Key Contribution(s) | Atomic Model/Concept |
| John Dalton | Developed the first modern atomic theory (elements are made of atoms, atoms of an element are identical, compounds form when atoms combine in fixed ratios). | Solid Sphere Model (Billiard Ball Model) |
| J.J. Thomson | Discovered the electron in 1897 using cathode ray experiments, proving atoms are divisible. | Plum Pudding Model (positively charged material with negatively charged electrons embedded) |
| Ernest Rutherford | Discovered the atomic nucleus (a tiny, dense, positively charged center) and that the atom is mostly empty space using the gold foil experiment. | Nuclear Model (electrons orbit a small, central nucleus) |
| Niels Bohr | Proposed that electrons orbit the nucleus in fixed, specific energy levels (shells), and can jump between these levels by absorbing or emitting energy (quanta). | Bohr Model (Planetary Model) |
| Erwin Schrödinger | Developed the quantum mechanical model of the atom using mathematical equations to describe the probability of finding electrons in certain regions of space. | Quantum Mechanical Model (Electron Cloud Model) |
| James Chadwick | Discovered the neutron in 1932, a neutral particle located in the nucleus, completing the basic picture of the atom's subatomic particles. | Contributed to the Quantum Mechanical Model |
