The chemical element with the highest electronegativity is fluorine. Positioned in group 17 of the periodic table, fluorine has a strong tendency to attract electrons, making it highly reactive. This electronegativity is due to its small atomic radius and the high effective nuclear charge, which allows it to exert a strong pull on electrons from other atoms during chemical bonding. The high electronegativity of fluorine contributes to its ability to form strong ionic and covalent bonds, influencing the reactivity and properties of its compounds significantly.