Based on:

Bromine: [Ar] 3d10 4s2 4p5
Iodine: [Kr] 4d10 5s2 5p5
Chlorine: [Ne] 3s2 3p5

what are the chemical property similarities based on the electron configuration?

1 answer

4p5, 5p5, 3p5 should tell you that all want to gain one electron to fill the outside shell. So all have an oxidation state of -1. If you will go to Google and type in chlorine, bromine, iodine,(individually) and scroll down on each to chemical properties, you will be able to write reactions for all that are essentially the same.