Q. The first and second ionisation enthalpies (in ) and the electron gain enthalpy (in ) of the elements , , , and are given below:
Element
520 7300 -60
419 3051 -48
1681 3374 -328
1008 1846 -295
2372 5251 + 48

The most reactive metal and the least reactive nonmetal of these are respectively

 2809  202 Classification of Elements and Periodicity in Properties Report Error

Solution:

I represents Li, II represents K, III represents Br, IV represents iodine, V represents He.
So, amongst these, II represents most reactive metal and V represents least reactive non-metal.