* J.J. Thomson's Cathode Ray Experiment: Thomson's experiments showed that cathode rays (which we now know are beams of electrons) were negatively charged particles.
* Atoms are Normally Neutral: Atoms are electrically neutral. This means they have no net charge. If atoms contain negatively charged electrons, there must be a balancing positive charge to maintain neutrality.
* The "Plum Pudding" Model: Thomson proposed the "plum pudding" model of the atom, which imagined a positively charged sphere with negatively charged electrons embedded within it. This model, though later disproven, helped explain the neutrality of atoms.
Later Discoveries:
* Rutherford's Gold Foil Experiment: Ernest Rutherford's famous experiment, where alpha particles were fired at a thin gold foil, showed that most particles passed through, but some were deflected at large angles. This led to the discovery of the nucleus, a dense, positively charged region at the center of the atom.
In summary: The discovery of negatively charged electrons, combined with the understanding that atoms are neutral, led scientists to deduce the existence of positive charges within atoms. Rutherford's work later confirmed this with the discovery of the positively charged nucleus.
