Which element has the lowest electronegativity?
Electronegativity decreases down a group and increases across a period. Among F, Cl, K, and Cs, Cs (group 1, period 6) has the lowest value.
Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Electron Gain Enthalpy and Electronegativity and Valency