Question

Arrange the elements I,F,Cl,Be increasing order of their electron gain enthalpy

Answer 1

Electron Gain Enthalpy is the energy change that occurs for the process of adding an electron to a gaseous isolated atom to convert it into  negative ion. In general, Electron gain enthalpy  become less negative in going from top to bottom in a group because as the size of atom increases, nuclear charge decreases and so the addition of electron becomes difficult.Electron gain enthalpy becomes more negative in going from left to right in a period due to decrease in size and thus increase in nuclear charge. 
P belongs to group 15, S belongs to group 16 and Cl,F belongs to group 17. The electron gain enthalpy should be greater in F as compared to Cl but it is less than that of Cl this is due to small size of F which leads to inter-electronic repulsion on addition of an electron i.e. electron density is high an the addition of electron is difficult. Therefore, order of increasing negative electron gain enthalpy is :

P<S<F<Cl

I hope it's helpful

Answer 2

Answer:

Chlorine gives highest electron gain enthalpy rather than flourine