Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
15.2k views
in Periodic Classification of Elements by (44.9k points)
closed by

Which of the following pairs of elements would have more negative electron gain enthalpy? 

1. O or F 

2. F or Cl.

1 Answer

+2 votes
by (45.7k points)
selected by
 
Best answer

1. O or F. Both O and F lie in 2e” period. As we move from O to F the atomic size decreases. Due to smaller size off nuclear charge increases. Further, gain of one electron by 

F → F- 

F- ion has inert gas configuration, While the gain of one electron by 

O → O- 

gives O ion which does not have stable inert gas configuration. Consequently, the energy released is much higher in going from

F → F- 

than going from O → O- . In other words electron gain enthalpy off is much more negative than that of oxygen.-

2. The negative electron gain enthalpy of Cl (e.g. ∆H = – 349 mol-1) is more than that of F (e.g. ∆H = -328 U mol-1 ). 

The reason for the deviation is due to the smaller size off. Due to its small size, the electron repulsion in the relatively compact 2p-subshell are comparatively large and hence the attraction for incoming electron is less as in the case of Cl.

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

...