The element francium has the lowest electronegativity is, with a reading of 0.8. Electronegativity is the measure of how much attraction an atom has for electrons and generally increases going toward the right of the periodic table and decreases going down the periodic table.
Because francium has the lowest electronegativity of all elements, it does not hang on to its electrons tightly. The element with the highest electronegativity on the periodic table is fluorine, which has a value of 4.0. Fluorine hangs on to its electrons tightly and, in fact, tries to take electrons from other atoms as well. Metals with low electronegativity, such as francium, belong to the group of elements called alkali metals. Nonmetals such as fluorine belong to the halogen group.