The strongest electropositive element is:

Electropositivity represents the tendency of an atom to lose electrons and form positive ions (cations). In the periodic table, electropositivity increases down a group because the atomic radius increases and the valence electrons experience a weaker nuclear attraction. Among the alkali metals, Cesium ($\text{Cs}$) has the largest atomic size and lowest ionization energy among the non-radioactive stable elements, making it the most strongly electropositive element listed.