Electronegativity is the ability of an atom of an element to attract electrons when the atom is in a compound. Did you know that scientists use factors such as ionization energy to calculate values for electronegativity. In general,electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period. Did you know that The least electronegative element in the table is Cesium, with an electronegativity value of 0.7 and the most electronegative is fluorine, with a level of 4.0.