Question

Assertion (A): Rutherford concluded that most of the mass of an atom is concentrated in a small region at the centre called the nucleus.

Reason (R): According to Thomson's model, electrons are embedded in a uniformly distributed positive charge sphere.

Options

• Both A and R are true, and R is the correct explanation of A.

• Both A and R are true, but R is not the correct explanation of A.

• A is true, but R is false.

• A is false, but R is true.

Answer 1

Both A and R are true, but R is not the correct explanation of A.

Explanation:

• Assertion (A) is true: Rutherford's gold foil experiment showed that most of the mass of an atom is concentrated in a small, dense, positively charged nucleus at its centre.
• Reason (R) is true: According to Thomson's atomic model, electrons are embedded in a sphere of uniformly distributed positive charge.

However, Thomson's model does not explain Rutherford's conclusion. Rutherford proposed the nuclear model based on the observations of his gold foil experiment.