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Question
Electronic configurations of four elements A, B, C and D are given below:
(A) 1s22s22p6
(B) 1s22s22p4
(C) 1s22s22p63s1
(D) 1s22s22p5
Which of the following is the correct order of increasing tendency to gain electron:
Options
A < C < B < D
A < B < C < D
D < B < C < A
D < A < B < C
Solution
A < C < B < D
Explanation:
(A) 1s22s22p6 – Noble gas configuration
(C) 1s22s22p63s1 – Requires one electron to complete 5-orbital
(B) 1s22s22p4 – 2 electrons short of stable configuration
(D) 1s22s22p5 – Requires one electron to attain noble gas configuration
• Noble gases have no tendency to gain electrons since all their orbitals are completely filled. Thus, element A has the least electron gain enthalpy.
• Since element D has one electron less and element B has two electrons less than the corresponding noble gas configuration, hence, element D has the highest electron gain enthalpy followed by element B.
• Since, element C has one electron in the 5-orbital and hence needs one more electron to complete it, therefore, electron gain enthalpy of C is less than that of element B. Combining all the facts given above, the electron gain enthalpies of the four elements increase in the order A < C < B < D.
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