Fluorine exhibits a higher electronegativity than iodine, primarily due to its smaller atomic radius and greater effective nuclear charge.

Electronegativity quantifies an atom’s ability to attract a bonding pair of electrons. This property is influenced by two key factors: atomic radius and effective nuclear charge. Although both fluorine and iodine belong to the halogen group in the periodic table, they display notable differences in their electronegativities. Notably, fluorine possesses the highest electronegativity of all elements, while iodine’s electronegativity is significantly lower.

The atomic radius refers to the distance from the nucleus’s center to the outer boundary of the surrounding electron cloud. Fluorine has a smaller atomic radius than iodine because, as one moves down a group in the periodic table, the number of electron shells increases, resulting in a larger atomic radius. The smaller atomic radius of fluorine means that its outer electrons are situated closer to the nucleus, leading to a stronger attraction to the center. This increased attraction enhances fluorine’s ability to attract a bonding pair of electrons, thereby contributing to its higher electronegativity.

Effective nuclear charge represents the net positive charge experienced by an electron in a multi-electron atom. In fluorine, the effective nuclear charge felt by the outermost electrons is greater than that experienced by their counterparts in iodine. This is due to fluorine having fewer electron shells, which reduces the shielding effect on the outer electrons from the nucleus compared to iodine. Consequently, the higher effective nuclear charge in fluorine results in a stronger attraction between the outer electrons and the nucleus, further elevating its electronegativity.

In conclusion, fluorine’s smaller atomic radius and higher effective nuclear charge lead to a stronger attraction for bonding electrons, rendering it more electronegative than iodine. Grasping these concepts is essential for predicting the properties of elements and their reactivity in chemical reactions.