The pair of elements most likely to form an ionic compound is Lithium and gold.
Ionic compounds typically form between metals and nonmetals. Lithium is a metal that can lose an electron to form a cation, while gold is also a metal and doesn't typically participate in ionic bond formation; rather, its bonding behavior is more covalent.
- Aluminum (a metal) and magnesium (also a metal) typically form metallic bonds rather than ionic bonds.
- Neon is a noble gas and is typically unreactive, so it won't form bonds with sulfur.
However, given the options provided, it should be noted that none of the pairs are highly likely to form ionic compounds, but Lithium (Li) as a metal could theoretically interact with other elements more easily than the rest in a simplistic sense of cation-anion interaction. Therefore, the correct choice is, interestingly, None of these, as a more accurate representation of likely ionic compounds.