To determine the compound formula for Li and X, we need to know the charges of the ions involved. Lithium (Li) is a group 1 element and typically forms a 1+ (Li+) ion. The element X could have various charges depending on its position in the periodic table.

Without knowing the specific charge of X, we can represent the compound formula as LiX. When the charges of the ions are known, we can determine the formula by balancing the charges. For example:

1. If X forms a 1- (X-) ion, the compound formula is LiX since the charges balance (1+ and 1-).

2. If X forms a 2- (X2-) ion, the compound formula is Li2X since two Li+ ions are needed to balance the charge of one X2- ion.

Determining the exact formula requires additional information about the element X and its charge.