Which element in group 17 has the highest tendency to form ionic compounds with group 1 elements?
Ionic character increases with larger electronegativity difference. F (highest electronegativity, 4.0) forms the most ionic compounds with group 1 elements (e.g., NaF) compared to Cl, Br, or I.
Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Electron Gain Enthalpy and Electronegativity and Valency