Which of the following represents the valence electron configuration for a bromine (Br) atom?

• A. 4s^2 4p^5
• B. 3s^2 3p^5
• C. 4s^2 3d^10 4p^5
• D. 2s^2 2p^5

Answer: (A)

Verified step by step guidance

1. Identify the atomic number of bromine (Br), which is 35. This tells us the total number of electrons in a neutral bromine atom.
2. Determine the electron configuration by filling orbitals in order of increasing energy using the Aufbau principle, Hund's rule, and Pauli exclusion principle.
3. Recognize that bromine's electrons fill up to the 3rd energy level completely and then start filling the 4th energy level orbitals.
4. Focus on the valence electrons, which are the electrons in the outermost shell (n=4 for bromine). These include the 4s and 4p orbitals.
5. Write the valence electron configuration for bromine as \$4s^2 4p^5$, since the 4s orbital is fully occupied with 2 electrons and the 4p orbital has 5 electrons.