Question

The first $(\Delta_i H_1)$ and second $(\Delta_i H_2)$ ionisation enthalpies (in $kJ\, mol^{-1}$) and the electron gain enthalpy $(\Delta_{eg} - H)$ (in $kJ\, mol^{-1}$) of the elements $I$, $II$, $III$, $IV$ and $V$ are given below:

Element	$\Delta_i - H_1$	$\Delta_i - H_2$	$\Delta_{eg} - H$
$I$	520	7300	-60
$II$	419	3051	-48
$III$	1681	3374	-328
$IV$	1008	1846	-295
$V$	2372	5251	+ 48

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

• A. I and V
• B. V and II
• C. II and V
• D. IV and V

Answer 1

Answer: (C)

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.