How a diatomic subscripts may differ from subscripts found in the formulas of compounds?

How can u compare the families and groups on the periodic table?

I don't really understand your questions. A diatomic molecule is one that has 2 substituant atoms in it (roughly: di = 2, atomic = atoms), what did you want to know about them?

The families and groups have different things is common, you can find out the significance of families and groups by reading up about the periodic table on Periodic table - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Periodic_table)

I think the word for "families" is "series", or it might refer to "block", you'd have to define "families" for me to be able to help you with that.