Which of the following represents the valence electron configuration for a sodium (Na) atom?

• A. 3p^1
• B. 3s^1
• C. 2s^2 2p^6
• D. 2s^2 2p^5 3s^2

Answer: (B)

Verified step by step guidance

1. Recall that the valence electrons are the electrons in the outermost shell (highest principal quantum number, n) of an atom.
2. Determine the atomic number of sodium (Na), which is 11, meaning it has 11 electrons in total.
3. Write the full electron configuration for sodium: 1s^2 2s^2 2p^6 3s^1.
4. Identify the valence shell by looking at the highest principal quantum number, which is n=3 for sodium, so the valence electrons are in the 3s orbital.
5. Conclude that the valence electron configuration for sodium is 3s^1, since the 3p orbital is empty and the 2s and 2p orbitals belong to the inner shells.