Why is this wrong?? You have been given a choice of four elements, Lithium, Magnesium, Sulfur, and Bromine. You must decide which two elements would form a compound that has two atoms of the metallic atom and one of the non-metallic atom in the final neutral compound. Which choice lists the two atoms with the correct formula for the compound?
Magnesium and Sulfur, Mg2S

Lithium and Sulfur, Li2S

Lithium and Bromine, Li2Br

Magnesium and Bromine, Mg2Br (THEY SAID THIS IS WRONG)