NEETChemistryp Block Elements (Group 15, 16, 17 & 18)
Assertion (A) : The bond dissociation energy increases from F 2 to Cl 2 and then decreases to I 2 Reason (R) : The low bond energy of fluorine is due to the repulsion between the lone pairs of electrons in two fluorine atoms. The correct option among the following is
Options
- A(A) is true, (R) is true and (R) is the correct explanation for (A)
- B(A) is true, (R) is true but (R) is not the correct explanation for (A)
- C(A) is true but (R) is false
- D(A) is false but (R) is true
Correct answer
A. (A) is true, (R) is true and (R) is the correct explanation for (A)
Step-by-step solution
Bond dissociation energy of F 2 molecule is less than that of Cl 2 molecule because F has smaller radius and due to smaller size repulsion is high. Both have 3 lone pairs but in the case of chlorine the lone pairs have more space to be in, leading to a lower stress on the bond. In Fluorine however the lone pairs have less space to be in, adding stress on the bond making its easier to break.