Question

electron gain enthalpy of F is less than cl

Answer 1

because size of F is very small so it is difficult for F to gain electron so electron gain enthalpy is more

Answer 2

The fluorine atom is smaller and has a higher effective nuclear charge than chlorine which result in very high inter-electronic repulsion amongelectrons of fluorine. This makes addition of electron unfavourable. Due to this electron gain enthalpy of fluorine is less negative than that ofchlorine.