The plum pudding model of the atom, proposed by J.J. Thomson in the early 20th century, primarily states that an atom is made up of electrons (negatively charged particles) embedded in a "sea" of positive charge, which balances the overall charge of the atom. Therefore, the correct statement regarding the plum pudding model is:
- An atom is made up of electrons in a sea of positive charges.
This model was an early attempt to explain the structure of the atom before the discovery of the nucleus and the subsequent development of more accurate atomic models.