Final answer:
The plum pudding model depicts the atom as a uniform positive sphere with electrons embedded within, whereas the nuclear model presents a centralized nucleus with electrons orbiting around it.
Step-by-step explanation:
The plum pudding model was an early conceptual model of an atom's structure. Proposed by J.J. Thomson in 1904 following his discovery of the electron, this model depicted the atom as a sphere of positive charge with negatively charged electrons embedded within it, much like plums in a pudding or blueberries in a muffin.
The positive charge was thought to be spread out throughout the atom, much like a cloud or jelly, and the electrons were considered somewhat mobile within this positive matrix.
Contrarily, the nuclear model of the atom was developed after Rutherford's famous gold foil experiment, which involved bombarding gold foil with alpha particles. The unexpected deflection of some particles suggested the presence of a small, dense, positively charged nucleus at the center of the atom, with electrons orbiting this nucleus.
This model represented a major departure from the plum pudding model, introducing the concept of a nucleus and thus modifying the understanding of atomic structure significantly.
In summary, while the plum pudding model suggested a uniform distribution of positive charge throughout the atom with electrons scattered within, the nuclear model introduced by Rutherford proposed a concentrated central nucleus, surrounded by electrons in defined orbits.
This critical evolution in atomic theory paved the way for the quantum mechanical model of the atom that we use today.