Here's why:

* Lithium (Li) is in group 1 of the periodic table, making it a +1 cation (Li⁺).

* Sulfur (S) is in group 16 of the periodic table, making it a -2 anion (S²⁻).

To balance the charges, you need two lithium ions (2 x +1 = +2) to combine with one sulfur ion (-2).