known as the halogens, exist as discrete, diatomic molecules. Highly reactive elements. Flourine is the most electronegative element. Flourine and chlorine exist as gases, bromine as a liquid and iodine as a solid.
Group seven begins with Manganese. Other elements in the group are: Technetium, Rhenium, and Bohruim. All of these have been classified at metallic substances.
If I had to guess I'd say it has something to do with maybe gasses an/or lights.(just a guess)
here is some info I found though.....
http://en.wikipedia.org/wiki/Group_7_element
A Group 7...