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:
A. Ar
B. Br
C. F
D. S
Choose the most appropriate from the options given below:
- (A)C > B > D > A
- (B)A > D > B > C✓ Correct
- (C)A > D > C > B
- (D)D > C > B > A
Answer: (B)
Solution
Electron gain enthalpy values (kJ/mol): F , S , Br , Ar .
Ordering from least favourable (most positive) to most favourable (most negative):
Argon, with a stable closed octet, strongly resists adding an electron (positive value). Fluorine has the most negative value among these despite its small size -- the small size does reduce the magnitude somewhat compared to what might otherwise be expected (electron-electron repulsion in the compact 2p subshell is why chlorine's electron gain enthalpy is even more negative than fluorine's), but among F, S, Br and Ar, fluorine still has the most negative value.
This gives the order A > D > B > C.
Ordering from least favourable (most positive) to most favourable (most negative):
Argon, with a stable closed octet, strongly resists adding an electron (positive value). Fluorine has the most negative value among these despite its small size -- the small size does reduce the magnitude somewhat compared to what might otherwise be expected (electron-electron repulsion in the compact 2p subshell is why chlorine's electron gain enthalpy is even more negative than fluorine's), but among F, S, Br and Ar, fluorine still has the most negative value.
This gives the order A > D > B > C.
JEE Main · 2024 · 31 Jan 2024 · Shift 1 · Single correct option