The orbital diagram for bromine shows four concentric circles around a dot representing a nucleus, with two dots on the first circle, eight on the second, 18 on the third and seven on the fourth. Each dot on a circle represents an electron.
The four concentric circles represent the four energy levels in which the electrons of a bromine atom sit. The diagram can also be expressed in a written configuration as 1s2 2s2p6 3s2p6d10 4s2p5. The first number of each grouping represents the same energy levels indicated by the diagram's circles, while the letters and following numbers describe the electron placement in different orbitals.