Assertion and reason

Exercise and reference answers

Questions

1. Reason

   It gave no account of why the revolving electron does not fall into the nucleus.

   Verdict

   Both are true; the reason explains the assertion.

   Assertion

   Rutherford's model could not explain atomic stability.

2. Reason

   A definite orbit requires exact position and exact velocity at once.

   Verdict

   Both are true; the reason explains the assertion.

   Assertion

   Bohr's model contradicts the uncertainty principle.

3. Reason

   Three quantum numbers describe each quantised energy state.

   Verdict

   The assertion is false and the reason is true.

   Assertion

   The quantum numbers must be assumed before solving.

4. Reason

   Alpha-particle scattering showed the mass is concentrated, not spread.

   Verdict

   Both are true; the reason explains the assertion.

   Assertion

   Thomson's model was abandoned.

Explanation