The correct sequence of electron gain enthalpy of the elements listed below is
A. Ar
B. Br
C. F
D. S
Choose the most appropriate from the options given below:

Solution

Chemistry ma’am · 3 steps

Rank the signed values: a positive value is the highest, and the most negative one comes last.

1. Read the sign. Electron gain enthalpy Δ_(eg)H is negative when energy is released on adding an electron. It is positive when energy must be supplied. "Greater" here means greater as a signed number, so a positive value beats every negative one.

   Element	Why	Δ_(eg)H (kJ mol⁻¹)
   A: Ar	Noble gas. The extra electron must enter a new, higher shell.	+96
   D: S	Needs two more electrons for an octet, so it attracts one moderately.	-200
   B: Br	Halogen, one electron short of an octet.	-325
   C: F	Halogen. Its small 2p shell causes repulsion, but it still releases slightly more energy than Br.	-328

2. Order them. From most positive to most negative: +96 > -200 > -325 > -328.
3. So. The sequence is Ar > S > Br > F, that is A > D > B > C, which is option (b).

The idea to keep. Compare electron gain enthalpies as signed numbers. Noble gases are positive, and F is less negative than Cl but still slightly more negative than Br.

Answer from the NTA final answer key. Solution by PrepWiser.