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:

विकल्प

• A < C < B < D

• A < B < C < D

• D < B < C < A

• D < A < B < C

Answer 1

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.