For a sodium atom (Na), in which principal energy level are the valence electron(s) found?

• A. n = 3
• B. n = 1
• C. n = 2
• D. n = 4

Answer: (A)

Verified step by step guidance

1. Recall that the principal energy level, denoted by the quantum number \(n\), corresponds to the main shell or energy level where electrons reside around the nucleus.
2. Determine the electron configuration of a sodium atom (Na), which has an atomic number of 11, meaning it has 11 electrons.
3. Write the electron configuration by filling orbitals in order of increasing energy: \$1s^2\(, \)2s^2\(, \)2p^6\(, and then \)3s^1$.
4. Identify the valence electrons as those in the outermost principal energy level, which is the highest \(n\) value occupied by electrons.
5. Since the last electron enters the \$3s\( orbital, the valence electron(s) of sodium are found in the principal energy level \)n = 3$.