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(A) most of the mass of the atom is conc...

(A) most of the mass of the atom is concentrated in its nucleus.
(R) all alpha particles striking a gold sheet are scattered in different directions.

A

if both assertion and reason are true and reason is the correct explanation of assertion.

B

if both assertion and reason are true but reason is not the correct explanation of assertion.

C

if assertion is true but reason is false.

D

if both assertion and reason are false.

Text Solution

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The correct Answer is:
To solve the assertion-reason question, we will analyze both the assertion and the reason step by step. ### Step 1: Analyze the Assertion The assertion states: "Most of the mass of the atom is concentrated in its nucleus." - The nucleus of an atom contains protons and neutrons, which are much more massive than electrons. - Since the mass of protons and neutrons accounts for nearly all of the atom's mass, this statement is true. ### Step 2: Analyze the Reason The reason states: "All alpha particles striking a gold sheet are scattered in different directions." - In the famous Rutherford gold foil experiment, it was observed that while some alpha particles were deflected at large angles, most passed through the foil with little or no deflection. - Therefore, it is incorrect to say that all alpha particles are scattered in different directions. Only a fraction of them are significantly scattered, particularly those that come close to the nucleus of the gold atoms. ### Step 3: Conclusion - The assertion is true: Most of the mass of the atom is indeed concentrated in its nucleus. - The reason is false: Not all alpha particles are scattered; only some are, and they are typically the high-energy ones. ### Final Answer - The assertion is true, and the reason is false.
To solve the assertion-reason question, we will analyze both the assertion and the reason step by step. ### Step 1: Analyze the Assertion The assertion states: "Most of the mass of the atom is concentrated in its nucleus." - The nucleus of an atom contains protons and neutrons, which are much more massive than electrons. - Since the mass of protons and neutrons accounts for nearly all of the atom's mass, this statement is true. ...
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