Which element in group 17 shows an anomaly in electron gain enthalpy compared to its neighbors?
F has less negative electron gain enthalpy than Cl due to electron repulsion in its compact 2p orbitals, an anomaly in group 17 trends where Cl > Br > I.
Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Electron Gain Enthalpy and Electronegativity and Valency