* Electronegativity Difference: Iron (Fe) has an electronegativity of 1.83, while sulfur (S) has an electronegativity of 2.58. The difference in electronegativity is significant (0.75), indicating a strong tendency for sulfur to attract electrons from iron.
* Metal and Nonmetal: Iron is a metal, and sulfur is a nonmetal. Metals tend to lose electrons, forming cations, while nonmetals tend to gain electrons, forming anions.
* Formation of Ions: In FeS, iron loses two electrons to form Fe²⁺ (iron(II) ion), and sulfur gains two electrons to form S²⁻ (sulfide ion).
Therefore, the strong electrostatic attraction between the oppositely charged ions (Fe²⁺ and S²⁻) is the defining characteristic of an ionic bond in FeS.
