Which of the following represents the valence electron configuration for a chlorine (Cl) atom?

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

Answer: (A)

Verified step by step guidance

1. Identify the atomic number of chlorine (Cl), which is 17. This means a neutral chlorine atom has 17 electrons.
2. Recall that electrons fill atomic orbitals in order of increasing energy levels, following the Aufbau principle: 1s, 2s, 2p, 3s, 3p, and so on.
3. Write the full electron configuration for chlorine by filling orbitals until you reach 17 electrons: 1s^2 2s^2 2p^6 3s^2 3p^5.
4. Determine the valence electrons by identifying the electrons in the outermost shell (highest principal quantum number n). For chlorine, the outermost shell is n=3, which includes 3s and 3p orbitals.
5. Express the valence electron configuration as 3s^2 3p^5, representing the electrons available for bonding and chemical reactions.