What is the element with the lowest electronegativity; calcium, helium, cesium, or fluorine?

Electronegavity is the ability of an atom to attract a shared pair of electrons in a covalent bond. Atoms with high electronegativities will attract more electrons and may occasionally steal electrons from other atoms. That said, electronegavity increases as you go across a period. I. e it increases as you move from left to right across a period on the periodic table but it decreases from top to bottom down a group. Generally non metal non-metals, located on the right side of the periodic table, have higher electronegativity. With that in mind caesium, a metal, which has an electronegativity of 0.79 is the least electronegative of them all.