Chapter 5 - Electron Configurations and the Periodic Table - Questions for Review and Thought - Topical Questions - Page 240c: 73b

$1s^22s^22p^63s^23p^63d^{10}4s^24p^6$

We write the electron configurations, using the information that we learned over the course of the chapter. The Bromide ion has one more electron than neutral Bromine. Recall, we start at 1s and move up: $1s^22s^22p^63s^23p^63d^{10}4s^24p^6$