Question

Assertion A: Electrons exist in sharp and specific orbits Reason R: The Schr\"odinger equation describes orbits as probability distributions In the light of the above statements, choose the most appropriate answer from the options given below
• Both A and R are correct and R is the correct explanation of A
• Both A and R are correct but R is NOT the correct explanation of A
• A is correct but R is not correct
• A is not correct but R is correct

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is NOT the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Modern quantum mechanics describes electrons using: \[ |\psi|^2 \] which gives probability density, not fixed orbits.

Answer 1

The Correct Option is D

Concept: Modern quantum mechanics replaced the classical Bohr picture of fixed electron orbits. According to wave mechanics: \[ \boxed{ \text{Electrons are described by probability distributions} } \] These regions are called orbitals.

Step 1: Analyze Assertion A. Assertion says: “Electrons exist in sharp and specific orbits” This statement belongs to Bohr's old atomic model. Modern quantum mechanics states:
• Exact electron path cannot be defined.
• Electron position is probabilistic. Therefore Assertion A is incorrect.

Step 2: Analyze Reason R. Reason says: “The Schr\"odinger equation describes orbits as probability distributions” This is essentially correct. Schr\"odinger wave equation gives: \[ \psi \] whose square: \[ |\psi|^2 \] represents probability density. Hence electrons are described by: \[ \boxed{ \text{Orbitals (probability clouds)} } \] not fixed orbits. Thus Reason R is correct.

Step 3: Determine the correct relationship. We find:
• Assertion is false.
• Reason is true. Therefore: \[ \boxed{ \text{A is not correct but R is correct} } \] Hence the correct option is: \[ \boxed{(4)} \] Final Conclusion: Electrons do not move in fixed sharp orbits; they are described by probability distributions. Hence, the correct answer is: \[ \boxed{(4)} \]