Neutron was not present in thomson model of atom since he has onl;y explained about the positive sphere and (protons) and electrons of   atom .

Neutron was not present in the thomson model as it was later discovered by James chardwick

Subatomic Particles Not Present in Thomson's Model of the Atom

In J.J. Thomson's model of the atom, also known as the "plum pudding" model, there are several subatomic particles that are not present. Thomson's model was proposed in the late 19th century before the discovery of many of these particles, so it is limited in its representation of the atom's structure. The subatomic particles not present in Thomson's model include:

1. Protons:
Thomson's model does not include protons, which are positively charged particles found in the nucleus of an atom. Protons were discovered later by Ernest Rutherford in his gold foil experiment in 1911. The presence of protons was crucial in understanding the atomic structure and the concept of atomic number.

2. Neutrons:
Similarly, Thomson's model also does not account for neutrons, which are electrically neutral particles found in the nucleus of an atom. Neutrons were discovered by James Chadwick in 1932. The existence of neutrons helps explain why atoms of the same element can have different masses (isotopes).

3. Electrons:
Although Thomson's model does include electrons, it does not accurately represent their distribution within the atom. According to Thomson's model, electrons are uniformly distributed throughout the positively charged "pudding" of the atom. However, later experiments and models, such as Rutherford's planetary model and Bohr's model, showed that electrons exist in specific energy levels or orbitals around the nucleus.

4. Quarks:
Thomson's model also does not account for quarks, which are elementary particles that make up protons and neutrons. Quarks were discovered in the 1960s and are considered to be the fundamental building blocks of matter. They have fractional electric charges and are bound together by the strong nuclear force.

Limitations of Thomson's Model:
Thomson's model of the atom had several limitations due to the lack of knowledge about the subatomic particles mentioned above. It failed to explain the existence of atomic mass variations, the discrete energy levels of electrons, and the overall structure of the atom. The subsequent discoveries of protons, neutrons, electrons' energy levels, and quarks provided a more accurate understanding of the atom's composition and behavior.