Within each pair of elements $\mathrm{F} \& \mathrm{Cl}, \mathrm{S} \& \mathrm{Se}$ and $\mathrm{Li} \& \mathrm{Na}$, respectively, the elements that release more energy upon an electron gain are

(D) $\mathrm{Cl}, \mathrm{S}$ and Li

(B) $\mathrm{Cl}, \mathrm{Se}$ and Na

JEE Main · 2020 · 07 Jan 2020 · Shift 2 · Classification of Elements and Periodicity

Within each pair of elements

F & Cl, S & Se

and

Li & Na

, respectively, the elements that release more energy upon an electron gain are

(A)F, Se and Na
(B) $Cl, Se$ and Na
(C)F, S and Li
(D) $Cl, S$ and Li✓ Correct

Answer: (D)

Solution

Electron gain enthalpy is most exothermic for the smaller member of a group once the first-row anomaly is allowed for. Chlorine releases more energy than fluorine, because fluorine's very compact

2 p

shell makes the incoming electron feel strong repulsion. Sulphur beats selenium, since on moving down a group the added electron sits farther out and less energy is freed. And lithium releases more than sodium for the same size reason. So the elements that give up more energy are chlorine, sulphur and lithium.

JEE Main · 2020 · 07 Jan 2020 · Shift 2 · Single correct option

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JEE Main · 2020 · 07 Jan 2020 · Shift 2 · Classification of Elements and Periodicity

Solution

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