Question

The first ${\Delta }_i{H}_1$ and second ${\Delta }_i{H}_2$ ionisation enthalpies in kJ mol${}^{-1}$ and the ${\Delta }_{eq}H$ electron gain enthalpy in kJ mol${}^{-1}$ of a few elements are given below :

	Elements	${\Delta }_i{H}_1$	${\Delta }_i{H}_2$	${\Delta }_{eg}H$
(A)	P	520	7300	-60
(B)	Q	419	3051	-48
(C)	R	1681	3374	-328
(D)	S	1008	1846	-295
(E)	T	2372	5251	+48
(F)	U	738	1451	-40

The least reactive element is :

• A. P
• B. Q
• C. R
• D. T

Answer 1

The correct option is D T

From the given data, it is visible that (${△}_i{H}_1$) and (${△}_i{H}_2$) for $T$ is maximum which means it is very difficult to take out an electron from $T$.

Also (${△}_{eg}H$) for $T$ is positive which resembles the value of a noble gas which is inert and least reactive.

Therefore, the correct option is D.