Electronic configurations of four elements A, B, C and D are given below: (A) 1s^(2)2s^(2)2p^(6) "" (B) 1s^(2)2s^(2)2p^(4) (C) s^(2)2s^(2)2p^(6)3s^(1) "" (D) 1s^(2)2s^(2)2p^(5) Which of the following is the correct order of increasing tendency to gain electron?

Electronic configurations of four elements A, B, C and D are given bel

1.	Electronic configurations of four elements A, B, C and D are given below: (A) 1s^(2)2s^(2)2p^(6) "" (B) 1s^(2)2s^(2)2p^(4) (C) s^(2)2s^(2)2p^(6)3s^(1) "" (D) 1s^(2)2s^(2)2p^(5) Which of the following is the correct order of increasing tendency to gain electron?
Answer» `A lt C lt B lt D` `A lt B lt C lt D` `D lt B lt C lt A` `D lt A lt B lt C` Solution :Electronic CONFIGURATION of elements indicate that A is a noble gas (i.e., Ne), B is oxygen (group 16), C is sodium metal (group 1) and D is fluorine (group 17). (i) Noble gases do not have tendency to gain electrons since all the orbitals are fully filled. Thus, element A is lowest ELECTRON gain enthalpy. (ii) Since, element D has one electron less than the corresponding noble gas configuration and element B has 2 electron less than the corresponding noble gas configuration. Element D has highest electron gain enthalpy then the element B. (iii) As, element C has only one electron in the S-orbital and hence need one more electron to complete it octet, therefore, electron gain enthalpy of C is less than that of B. Combining all the above information, the electron gain enthalpy in increasing order for the four elements is `A lt C lt B lt D`