A: Electronic energy for hydrogen atom of different orbitals follow the sequence
` 1s lt 2s = 2p lt 3s = 3p = 3d`
R : Electronic energy for hydrogen atom depends only on n and is independent of 'l' & 'm' values .

Options

A. IF both assertion & reason are true and the reason is the correct explanation of the assertion then mark
B. IF both assertion & reason are true but the reason is not the correct explanation of the assertion , then mark
C. IF assertion is true statement but reason is false , then mark
D. If both assertion and reason are false statements then mark

Answer

To solve the question, we need to analyze the assertion (A) and the reason (R) provided regarding the electronic energy levels of the hydrogen atom.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that the electronic energy for hydrogen atom orbitals follows the sequence:
\( 1s < 2s = 2p < 3s = 3p = 3d \).
- This means that the energy levels increase as we move from \( 1s \) to \( 2s \), and within the second shell, \( 2s \) and \( 2p \) have the same energy. Similarly, for the third shell, \( 3s \), \( 3p \), and \( 3d \) have the same energy.

2. **Understanding the Reason (R)**:
- The reason states that the electronic energy for hydrogen atom depends only on the principal quantum number \( n \) and is independent of the azimuthal quantum number \( l \) and the magnetic quantum number \( m \).
- This means that for hydrogen, the energy levels are determined solely by the value of \( n \), and not by the values of \( l \) or \( m \).

3. **Analyzing the Energy Levels**:
- For hydrogen, which is a one-electron system, the energy levels are determined only by the principal quantum number \( n \).
- As \( n \) increases, the energy increases. Thus, \( 1s \) has the lowest energy, followed by \( 2s \) and \( 2p \) (which are equal), and then \( 3s \), \( 3p \), and \( 3d \) (which are also equal).

4. **Conclusion**:
- Both the assertion and the reason are true. The reason correctly explains why the assertion is true, as the energy levels for hydrogen depend only on \( n \) and not on \( l \) or \( m \).

5. **Final Answer**:
- Therefore, the correct option is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.