Question

Give one achievement and one limitation of J.J Thomson's model of atom?

Answer 1

J.J. Thomson was the first to propose a detailed model of an atom.

J.J. Thomson's model of an atom:

1. In 1898, Thomson proposed that an atom consists of a uniform sphere of positive charge in which negatively charged electrons are embedded.
2. Thomson assumed that the mass of atom is uniformly distributed over the atom.
3. Thomson compared the atom to a watermelon or plum pudding.
4. In watermelon, seed were compared to electrons and the entire red portion was compared to a positive sphere.
5. In plum pudding, raisins were compared to electrons and the entire pudding was compared to a positive sphere.

Achievement of J.J. Thomson's model of an atom:

Thomson's said that the positive and negative charges in an atom are equal and balance each other. Thus, the model explained electrical neutrality of an atom.

Drawbacks of J.J. Thomson's model of an atom:

1. Thomson's model did not give mass of an electron.
2. It did not explain Rutherford's alpha particle scattering experiment.