Give the symbols for 4 species that are isoelectronic with the bromide ion, br-

Isoelectronic means that the species have the same number of electrons as the bromide ion, which has 36 electrons. Considering ions of the charge - 2, + 1, + 2 and neutral atoms,

Krypton (Kr)

Selenium - 2 (Se-2)

Rubidium + 1 (Rb+)

Strontium + 2 (Sr+2)

All have 36 electrons, which means they are isoelectronic with the bromide ion.