Which of the following statements about Thomson's model of an atom is/are correct? Statement 1: An atom consists of a positively charged sphere with electrons embedded in it. Statement 2: The mass of the atom is due to neutrons located in the nucleus. Statement 3: The model is often compared to a watermelon, with seeds representing electrons.

J.J. Thomson proposed that the atom is a uniform sphere of positive electricity in which negatively charged electrons are distributed to maintain electrical neutrality. The model is famously nicknamed the 'Plum Pudding' or 'Watermelon' model, where the red pulp represents the positive charge and the seeds represent the electrons. J.J. Thomson discovered the electron through his experiments with cathode ray tubes, for which he won the Nobel Prize in Physics in 1906. Thomson's model was eventually disproved by Ernest Rutherford's gold foil experiment, which showed that the positive charge is concentrated in a tiny central nucleus rather than spread throughout the atom. Statement 2 is incorrect because the nucleus (and hence neutrons) had not yet been discovered in Thomson's model.