Which of the following will have the most negative and the least negative electron gain enthalpy ? P,S,Cl,F. Explain your answer.

Explanation

Electron gain enthalpy generally becomes more negative across a period as we move from left to right within a group electron gain enthalpy becomes less negative down the group . However adding an electron to the 2 p orbital leads to greater repulsion than adding an electron to the larger 3 p orbital . Hence the most negative electron gain enthalpy is of chlorine and the negative electron gain enthalpy is of phoshporus .