Objections to Thomson model of an atom:
i) It is only a proposal without any valid experimental observation.
ii) Cathode ray experiments with perforated anode showed that the canal rays as positively charged particles with definite mass and the e/m values changing with the gas present in the tube. The positive charged particle is different for different gases and is characteristic of the gas involved.
Hence, consideration of the positive charge as a diffused cloud and that too in the form a sphere is totally is untenable.
iii) The model treats the charges both positive charge as static in the sphere of atom. Opposite charges attract each other. This will make the opposite charge get closer and ultimately annihilate each other. Such an atom will be unstable due to the forces of attraction between the opposite charges.
Hence there has to be empty space between the oppositely charges and some forces to keep them apart permanently to avoid such collision and annihilation.
iv) Thomson model of atom, will not explain many properties of electron, proton and that were observed experimentally. Thomson model will not explain for example –
a) Presence of small positively charged nucleus
b) Photoelectric effect of atoms
c) Wave nature of electron
d) Characteristic atomic spectra and
e) Radioactivity etc.