The correct order of first ionization enthalpy values of the following elements is:

(A) O
(B) N
(C) Be
(D) F
(E) B

Question

The correct order of first ionization enthalpy values of the following elements is:

(A) O 
(B) N
(C) Be 
(D) F 
(E) B

Canvas Classes · Accepted Answer

Strategy:
 First ionization enthalpy () generally increases across a period. Key exceptions occur due to the stability of half-filled () or fully filled () subshells.

Step 1: Compare elements across Period 2
Elements:  (Grp 2),  (Grp 13),  (Grp 15),  (Grp 16),  (Grp 17).
General Trend: .

Step 2: Apply configuration stability rules
-  () vs  (): Removing an electron from a filled  subshell requires more energy than from the  subshell. Thus, .
-  () vs  (): Nitrogen's half-filled -subshell is mo

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