Everything Is Made of Atoms

Plum Pudding Model

The Plum Pudding Model, proposed by J.J. Thomson, was an early attempt to describe the structure of the atom. Thomson suggested that atoms consisted of a positively charged substance with negatively charged electrons embedded within, akin to raisins in a plum pudding. However, this model was soon challenged by new discoveries, particularly the work of Ernest Rutherford, who demonstrated that atoms have a small, dense nucleus.

With this new discovery, Thomson created a new theory of the atom, which was dubbed the plum pudding theory. This theory held that there was a positively charged substance that the negatively charged electrons were embedded within, just like how raisins were embedded in plum pudding.

--- Gary Arndt

Thomson's model was eventually replaced by Rutherford's nuclear model, which introduced the concept of a central nucleus surrounded by orbiting electrons 1.

   

Rutherford's Gold Foil

Ernest Rutherford's gold foil experiment was pivotal in reshaping atomic theory by introducing the idea of a dense nucleus. By firing alpha particles at a thin gold foil, Rutherford observed that some particles were deflected at unexpected angles, suggesting the presence of a dense, positively charged center within the atom. This discovery led to the development of a new atomic model, where electrons orbit a central nucleus, similar to planets around the sun.

Rutherford realized this could only have happened if two things were true. The first was that there was an extremely dense, positively charged nucleus to the atom that was reflecting some of the alpha particles back.

--- Gary Arndt

Rutherford's findings laid the groundwork for future advancements in atomic theory, including Niels Bohr's model, which further refined the understanding of electron orbits 1.