What is the smallest possible value of the principal quantum number (n) for an electron in an atom?

• A. 1
• B. -1
• C. 0
• D. 2

Answer: (A)

Verified step by step guidance

1. Understand that the principal quantum number, denoted as \(n\), describes the main energy level or shell of an electron in an atom.
2. Recall that \(n\) must be a positive integer because it represents quantized energy levels starting from the closest shell to the nucleus.
3. Recognize that the smallest possible value of \(n\) is 1, which corresponds to the first energy level (also called the K-shell).
4. Note that values like 0 or negative integers are not allowed for \(n\) because they do not correspond to physical energy levels in quantum mechanics.
5. Therefore, the smallest valid principal quantum number for an electron in an atom is \(n = 1\).