* Dalton's Atomic Theory (1803): John Dalton proposed that atoms were tiny, indivisible, solid spheres. This model focused on the idea of atoms as the basic building blocks of matter, but didn't account for the internal structure of the atom.
* Thomson's Plum Pudding Model (1897): J.J. Thomson discovered the electron and proposed a model where the atom was a positively charged sphere with negatively charged electrons embedded within it, like plums in a pudding. This model still had a solid sphere at its core, but it introduced the idea of subatomic particles.
These early models were based on the limited scientific knowledge of the time. However, the discovery of the nucleus and the development of quantum mechanics in the early 20th century led to more accurate and complex models of the atom, which no longer relied on the concept of a solid sphere.
