Which of the following electronic transitions within a hydrogen atom is not possible?

• A. An electron moves from n = 1 to n = 1
• B. An electron moves from n = 2 to n = 1
• C. An electron moves from n = 4 to n = 3
• D. An electron moves from n = 3 to n = 2

Answer: (A)

Verified step by step guidance

1. Understand that electronic transitions in a hydrogen atom involve an electron moving between energy levels denoted by the principal quantum number \( n \).
2. Recall that a transition means the electron changes its energy state, so the initial and final \( n \) values must be different for a transition to occur.
3. Examine each option to see if the electron moves from one energy level to a different one:
4. - For \( n = 1 \) to \( n = 1 \), the electron stays in the same energy level, so no transition occurs.
5. - For the other options (\( n = 2 \) to \( n = 1 \), \( n = 4 \) to \( n = 3 \), and \( n = 3 \) to \( n = 2 \)), the electron moves between different energy levels, which are valid transitions.