Import Question JSON

$\text{HINT: The concept of the Fajan rule is used.}$ $\text{Explanation:}$ $\text{In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively charged anion.}$ $\text{Ionic bonds require an electron donor, often a metal, and an electron acceptor, a nonmetal.}$ $\text{Using Fajan's rule, a larger cation and smaller anion will have maximum ionic character.}$ $\text{Hence, Cs is the most electropositive element in the first group, and F is the most electronegative element.}$ $\text{So, they will form the most ionic compound CsF.}$ $\text{To maximize the ionic character of a compound, we need the largest possible difference in electronegativity between the combining elements.}$ $\text{Electronegativity generally decreases down a group and increases across a period.}$ $\text{Among the given options:}$ $\text{Metals: Na (Sodium) and Cs (Cesium). Cesium (Cs) is below Sodium (Na) in Group 1, making it more electropositive and having lower ionization enthalpy, thus a larger cation.}$ $\text{Non-metals: F (Fluorine) and I (Iodine). Fluorine (F) is above Iodine (I) in Group 17, making it more electronegative and having higher electron gain enthalpy, thus a smaller anion.}$ $\text{Therefore, the combination of the most electropositive metal (Cs) and the most electronegative non-metal (F) will result in the compound with the maximum ionic character.}$ $\text{This corresponds to Cesium and Fluorine forming CsF.}$