Determine how many protons, neutrons, and electrons are in a bromine atom that has a mass number of 73

Br-73

The 73 means that the number of protons + neutrons = 73

We can find the number of protons by looking at a periodic table as that is unique to each element. Bromine has 35 protons. 

It will have 73 - 35 = 38 neutrons.

Since this is a neutral element, the number of electrons will be equal to the number of protons. It will have 35 electrons.

35 protons, 38 neutrons, 35 electrons.