Final answer:
Fluorine is the most electronegative element with an electronegativity value of 3.98. Electronegativity increases from the bottom left to the top right of the periodic table, and fluorine is found at the upper rightmost corner.
Step-by-step explanation:
The student asked which atom is the most electronegative. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Pauling's scale is commonly used to compare the electronegativity of different elements. Based on the information provided, fluorine (F) with an electronegativity value of 3.98 is the most electronegative element. This value is higher compared to any other element on the periodic table. The ranking of electronegativity generally increases as you move from the bottom left corner to the top right corner of the periodic table. Cesium (Cs), on the other hand, is indicated as the least electronegative nonradioactive element, with an electronegativity value of 0.79.
In molecules, usually, the least electronegative atom is found in the central position, with two exceptions mentioned: hydrogen and the halogens, such as fluorine, tend to be terminal atoms. This is relevant when predicting the structure of molecules such as CHO₂⁻, POCl₃, SO₂, and ClO₄⁻.