JEE MainChemistryClassification of Elements and Periodicity in Properties
Negative electron gain enthalpy values of the first four group 17 elements are given below. Choose the correct value for the element that exists as a liquid at room temperature :
Options
- A349 ~kJ ~mol ⁻¹
- B333 ~kJ ~mol ⁻¹
- C296 ~kJ ~mol ⁻¹
- D325 ~kJ ~mol ⁻¹
Correct answer
D. 325 ~kJ ~mol ⁻¹
Step-by-step solution
The first four elements of group 17 are F, Cl, Br, and I. Among these, Bromine (Br) exists as a liquid at room temperature. The negative electron gain enthalpy generally decreases down the group, but Fluorine has a lower value than Chlorine due to its small size and high interelectronic repulsions. The correct order of negative electron gain enthalpy is Cl > F > Br > I . Assigning the given values in decreasing order: Cl = 349 ~kJ ~mol ⁻¹ F = 333 ~kJ ~mol ⁻¹ Br = 325 ~kJ ~mol ⁻¹ I = 296 ~kJ ~mol ⁻¹ Thus, the value