The inner shell to which the electrons jump from the outer shells in the formation of Pfund series in the hydrogen spectrum is

Explanation

To solve the question regarding the Pfund series in the hydrogen spectrum, we need to identify the inner shell to which electrons jump from the outer shells. Here’s a step-by-step solution:

### Step 1: Understand the Pfund Series
The Pfund series is a set of spectral lines in the hydrogen spectrum that corresponds to electronic transitions. Specifically, it involves transitions where electrons fall from higher energy levels (outer shells) to a lower energy level.

### Step 2: Identify the Energy Levels
In the hydrogen atom, the energy levels are denoted by the principal quantum number \( n \). The Pfund series involves transitions to the \( n = 5 \) level. This means that the inner shell (where the electron falls to) is \( n = 5 \).

### Step 3: Determine the Outer Shells
The outer shells from which the electrons can jump to the \( n = 5 \) level are \( n = 6, 7, 8, 9, \) etc. Therefore, the electrons transition from these higher energy levels down to the \( n = 5 \) level.

### Step 4: Conclusion
Since the question asks for the inner shell to which the electrons jump, we conclude that the inner shell is \( n = 5 \).

### Final Answer
The inner shell to which the electrons jump in the formation of the Pfund series in the hydrogen spectrum is **5**.

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