Here's how to figure out the number of electrons in a bromide ion:

* Bromine's Atomic Number: Bromine (Br) has an atomic number of 35, meaning a neutral bromine atom has 35 protons and 35 electrons.

* The Bromide Ion: A bromide ion (Br-) has gained one electron.

* Total Electrons: Therefore, a bromide ion has 35 + 1 = 36 electrons.