Choose the correct option from the following options given below :

This question compares Rutherford's nuclear model with Thomson's plum pudding model of the atom.

Analyzing each option:

Option A: In Rutherford's model, electrons orbit the nucleus. An orbiting electron undergoes centripetal acceleration. According to classical electrodynamics, an accelerating charge radiates energy, so the electron is NOT in stable equilibrium. In Thomson's model, electrons sit at equilibrium positions inside a uniform positive charge distribution, where they can be in stable equilibrium. This option has it backwards. Incorrect.

Option B: In Thomson's model, the positive charge (and mass) is uniformly distributed throughout the atom — so the mass distribution is nearly continuous. In Rutherford's model, most mass is concentrated in a tiny nucleus — highly non-uniform. This option has it backwards. Incorrect.

Option C: In Rutherford's model, the electron orbits the nucleus in a circular or elliptical path. According to classical electromagnetic theory, an accelerating charged particle (the orbiting electron) must continuously radiate electromagnetic energy. As the electron loses energy, it spirals inward and eventually collapses into the nucleus. Therefore, a classical atom based on Rutherford's model is indeed doomed to collapse. This is correct.

Option D: In Rutherford's model, most of the mass is concentrated in the nucleus (positively charged part) — this is correct. However, in Thomson's model too, the positively charged sphere carries most of the mass (since proton mass >> electron mass). So this statement is misleading/incorrect in claiming "but not in Thomson's model."

The correct answer is Option C.