The correct answer is option 'D' - the nuclear model. Let's understand why this model is different from Thomson's model of the atom.

Thomson's Model of Atom:
- Proposed by J.J. Thomson in 1904, it is also known as the "plum pudding model" or "raisin pudding model."
- According to this model, the atom is composed of a positively charged sphere with negatively charged electrons embedded within it, much like raisins in a pudding or plums in a pudding.
- The positive charge and negative charge are evenly distributed throughout the atom, resulting in a neutral overall charge.

Now, let's understand why the nuclear model is different from Thomson's model:

Nuclear Model:
- Proposed by Ernest Rutherford in 1911, the nuclear model of the atom is also known as the Rutherford model or planetary model.
- According to this model, the atom consists of a small, dense, positively charged nucleus at the center, which contains most of the atom's mass.
- Electrons revolve around the nucleus in specific energy levels or orbits, similar to planets orbiting the sun.
- The nucleus is positively charged due to the presence of protons, while the electrons are negatively charged.
- The rest of the atom is mostly empty space.

Difference between the two models:
The main difference between Thomson's model and the nuclear model lies in the distribution of positive charge within the atom:

- In Thomson's model, the positive charge is spread throughout the atom, while the electrons are embedded within it. It does not have a concentrated nucleus.
- In the nuclear model, the positive charge is concentrated in a small, dense nucleus at the center of the atom. The electrons revolve around this nucleus.

Overall, the nuclear model proposed by Rutherford is an advancement over Thomson's model as it provides a more accurate understanding of the atom's structure.