Which of the following is the correct electron configuration for the bromide ion, Br−?

• A. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^3
• B. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5
• C. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6
• D. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^4

Answer: (C)

Verified step by step guidance

1. Identify the atomic number of bromine (Br), which is 35. This means a neutral bromine atom has 35 electrons.
2. Since the problem asks for the electron configuration of the bromide ion (Br⁻), remember that the ion has gained one extra electron, so it has 36 electrons in total.
3. Write the electron configuration for 36 electrons by filling the orbitals in order of increasing energy using the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, 3d, and then 4p orbitals.
4. Distribute the 36 electrons according to the maximum capacity of each subshell: 1s (2), 2s (2), 2p (6), 3s (2), 3p (6), 4s (2), 3d (10), and 4p (6).
5. Confirm that the final electron configuration ends with 4p^6, indicating a full p subshell in the fourth energy level, which corresponds to the bromide ion's electron configuration.