What could be the forth quantum number for one of the electrons in the 4p energy sublevel of bromine?

The fourth quantum number is the spin quantum number (ms), which can have a value of either +1/2 or -1/2. For the 4p energy sublevel of bromine, which has the electron configuration [Ar] 4s² 3d¹⁰ 4p⁵, one of the electrons in the 4p sublevel can have a spin quantum number of either +1/2 or -1/2, depending on its specific spin orientation. Thus, either value is possible for the spin of an electron in this sublevel.