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The plum pudding model was J.J. Thomson's earliest atomic model, proposed in 1904. In this model, the atom is imagined as a 'pudding' of positive charge, within which the negatively charged electrons (like 'plums') are scattered. This analogy helps visualize the distribution of electrons encased in a field of positive charge. Thomson proposed this model to explain how atoms could be neutral overall, despite containing negatively charged electrons. The positive 'pudding' balances the negative charges of the electrons, resulting in an electrically neutral atom. This model marked a significant step in atomic theory, although it was later replaced by more accurate models.

Electrons are tiny, negatively charged particles that exist outside the nucleus of an atom. They are fundamental components of atoms and play a crucial role in chemical reactions and bonds. Discovered by J.J. Thomson in 1897 through his work with cathode rays, electrons helped scientists understand the internal structure of atoms. According to Thomson's plum pudding model, electrons are embedded within a positively charged 'pudding' or 'soup'. This arrangement helps maintain the electrical neutrality of the atom. The discovery of electrons revealed that atoms are divisible and contain smaller subatomic particles, challenging the previously held belief that atoms were indivisible.

Cathode rays are streams of electrons that can be observed in vacuum tubes when a high voltage is applied. These rays were crucial in the discovery of the electron and the development of atomic models. In Thomson's experiments, he found that cathode rays were deflected by electric and magnetic fields, indicating that they carried a negative charge. According to Thomson's model, the atoms had electrons that could be knocked out under certain conditions. When high voltage is applied across the vacuum tube, these electrons are emitted from the cathode (negative electrode) and travel toward the anode (positive electrode). This movement creates cathode rays, demonstrating the presence of electrons within atoms. This discovery was vital for advancing our understanding of atomic structure.