[milind]

There are some pairs of non metals given below, please tell which one in each pair is more reactive than the other...

1. Cl, O
2. Br, N
3. I, C
4. Br, S
5. N, S
6. I, P
7. C, P
8. I, Se
9. P, Se
10. C, Se
11. At, C
12. At, P
13. At, Se
14. C, S
15. Cl, N

[Arkcon]

Per forum rules you should show your attempts at solving the problem before receiving help.

Briefly, your question is pretty tedious.   You have 41 separate questions, with redundant entries across them.  You would be better off if you learned what concepts underlie the reactivities, and just sorted them all.

[Borek]

Won't hurt to define "reactive".

14 is C and S. I should have a piece of carbon and piece of sulfur somewhere here. Both are quite stable.

(If I don't have them, it is not because they reacted with anything, but because I lost them).

[milind]

Well, this is not my homework or something but we were learning Chemical Reactions and as for a need to make things easier were trying to make up a reactivity series of the 12 non metals, which are; H, C, N, O, F, P, S, Cl, Se, Br, I, At; if someone can tell in order from the Highest reactive non metal till the lowest in these that would even be better and that is exactly what we want as we still don't have enough knowledge to form up a reactivity series of the elements.

[Borek]

It won't work this way. You can easily compare F, Cl, Br, I and At, as their chemistry is quite similar, but you can't easily compare H and O, as their chemistry is quite different.