Question

Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species?
A. $Cl < F < S < O$
B. $O < S < F < Cl$
C. $S < O < Cl < F$
D. $F < Cl < O < S$

Answer 1

Hint: The electron gain enthalpy can be elaborated as the amount of energy released or absorbed when an electron is added to an isolated gaseous atom. During this process of the addition of an electron, the energy can be absorbed or released. Hence, one can apply this concept and find the correct order of atomic species in options.

Complete step by step answer:
- First of all we will learn about the concept of negative electron gain enthalpy which can be elaborated as the amount of energy released when an electron is added to an isolated gaseous atom.
-Now let's discuss the electron gain enthalpy of each element given in the options one by one. The chlorine atom has high electron gain enthalpy because of its large size.
-In the fluorine atom due to its small size there is very high electronic repulsion among the electrons of fluorine which makes the addition of another electron very difficult.
- The sulfur atom has high electron gain enthalpy because of larger size and lower electron density which is the case of oxygen atom it is low due to small size.
Therefore, the order of electron gain enthalpy is $O < S < F < Cl$ which shows option B as the correct choice.

Note: The negative sign of electron gain enthalpy indicates that the energy is released when an electron is added to the element. The electron gains enthalpy very much dependent on the size of the element in which the bigger the higher the electron gains enthalpy but less negative electron gain enthalpy. The electron gain enthalpy increases in a period moving from left to right but decreases in a group on moving towards down. Therefore the halogen elements show a very high electron affinity.