Which of the following represents the electron configuration of S^{2-}?

• A. 1s^2 2s^2 2p^6 3s^2 3p^4
• B. 1s^2 2s^2 2p^6 3s^2 3p^6
• C. 1s^2 2s^2 2p^6 3s^2 3p^5
• D. 1s^2 2s^2 2p^6 3s^2 3p^2

Answer: (B)

Verified step by step guidance

1. Identify the atomic number of sulfur (S), which is 16. This means a neutral sulfur atom has 16 electrons.
2. Determine the electron configuration of neutral sulfur by filling orbitals in order of increasing energy: 1s, 2s, 2p, 3s, and then 3p.
3. Write the electron configuration for neutral sulfur: \$1s^2 2s^2 2p^6 3s^2 3p^4$, since the last 4 electrons go into the 3p orbital.
4. Recognize that the ion S^{2-} has gained 2 extra electrons compared to neutral sulfur, increasing the total number of electrons to 18.
5. Add the 2 extra electrons to the 3p orbital, filling it completely to 6 electrons, resulting in the electron configuration: \$1s^2 2s^2 2p^6 3s^2 3p^6$.