Question: how many electrons are there in the fourth quantum shell of a bromine atom?
Answer: So, bromine is located in period 4, group 17 of the periodic table and has an atomic number equal to 35 . This tells you that a neutral bromine atom has a total of 35 electrons surrounding its nucleus. Notice that bromine's outermost electrons, i.e. its valence electrons, are located on the fourth energy level, n=4 .