Electronegativity trends in periodic table. Animation showing the trends in the values of electronegativity across periods and down groups in the periodic table. The elements are shown as 3D cubes with larger cubes showing a larger electronegativity. For an element, electronegativity is the ability of an atom to attract electrons. This affects the chemical reactivity of an element and the nature of the chemical bonds it forms. In general, electronegativity increases from left to right along a period, and decreases from top to bottom down a group. This is shown in the animation by panning across the periods, focusing on fluorine (the most electronegative element), and then panning down that group. Caesium (the least electronegative element) is at lower left.