Which element is the most reactive non metal?
I'd have to go with fluorine.
The most reactive goup in the metals is the Alkali metals (Group I) The most reactive non-metal group is Group 17 or VIIA) the Halogens. It is difficult to say which of the two groups is more reactive. Chemists will say that Flourine is the most reactive element. Note that Group 18 is the least reactive, most stable.