The bond formed between aluminum (Al) and sulfur (S) is primarily ionic. This is due to the significant difference in electronegativity between the two elements. Aluminum is a metal and tends to lose electrons, while sulfur is a nonmetal that tends to gain electrons.
When aluminum reacts with sulfur, it donates three electrons to achieve a stable electron configuration, forming Al3+ ions. Sulfur, on the other hand, gains those electrons to form S2- ions. The electrostatic attraction between the positively charged aluminum ions and negatively charged sulfur ions results in the formation of an ionic bond.
Although one might consider whether the bond is polar or nonpolar covalent, in this scenario, the characteristic properties of ion formation and charge transfer indicate that the bond is ionic rather than covalent. In summary, the bond between aluminum and sulfur exhibits ionic characteristics due to the transfer of electrons caused by their differing electronegativities.