Final answer:
J.J. Thomson's experiments with cathode ray tubes led to the discovery of electrons and the development of the 'plum pudding' model of the atom, characterizing electrons embedded in a positively charged sphere.
Step-by-step explanation:
Discovery of the Electron and Thomson's Atomic Model
In 1897, J.J. Thomson conducted experiments that led him to propose a new model for the atomic structure. Thomson used a device called a cathode ray tube, where he observed streams of particles emanating from the cathode. These particles, which he called 'corpuscles,' bent when subjected to magnetic and electric fields, suggesting that they had charge and mass. Thomson is credited with the discovery of these particles, which we now call electrons.
Given the known neutrality of atoms and the negative charge of electrons, Thomson needed to account for a positive charge to balance the electron's negative charge. He hypothesized that electrons were embedded in a uniform sphere of positive charge akin to plums in a pudding. This model was famously coined the 'plum pudding' model of the atom, where the 'pudding' represented the positive charge and the 'plums,' the electrons.
Thomson's atomic model provided a foundation for understanding atomic structure at a time when the concept of subatomic particles was still emerging. It accounted for neutrality in atoms and allowed for the existence of ions by suggesting electrons could be gained or lost. However, it would later be revised by Ernest Rutherford's gold foil experiment, which refuted the idea of a uniform positive sphere and replaced it with the concept of a concentrated nucleus.