Br- < Se2- < As3- < Sr2+ < Rb+
I hope this helps although I'm not a hundred percent sure!
Remember the order, <n, l, ml, and ms>.
n: energy level
l: subshell
ml: number of orbitals in the subshell.
ms: electron spin.
The first numbers (n) of both the electrons are the same, but the only difference is the second number (l). The first electron has l=2, indicating that the electron is in the "d" subshell. On the other hand, the second electron has l=1, indicating that the electron is in the "p" subshell.
*Remember*
l=0 (s) spherical shape
l=1 (p) peanut shaped
l=2 (d) clover
A. Magnetic force is an non-contact force
The best way to determine the presence of halogens is by adding a silver nitrate solution to the solvent. This is because all halogens, except for fluorine, produce a precipitate with silver nitrate solution.
Chlorine produces a white precipitate, bromine produces a pale cream colored precipitate and iodine produces a yellow colored precipitate.
If further testing is required, concentrated sulfuric acid may be added. The sulfuric acid will produce misty fumes with fluorine and chlorine, brown fumes with bromine and purple fumes with iodine.