In short 2NaI + Br2------> 2NaBr + I2
The balanced equation of bromine plus sodium iodide yields sodium bromide plus iodine is;2NaI + Br2 ------> 2NaBr + I2Two moles of sodium iodide react with one mole of bromine to form two moles of sodium bromide and one mole of iodine. Iodine and bromine are halogens and sodium is an alkali metal.
Halogens have seven electrons in their outermost shell and alkali metals have one electron in their valence shell. So, alkali metals lose one electron and halogens gain this electron to form salts.