Final answer:
The Lewis structure for Li and S in the compound lithium sulfide shows Li with a '+', having lost one electron, and S with 2 '-', having gained two electrons. The formula of the ionic compound formed between Li+ and S2- ions is Li2S.
Step-by-step explanation:
To draw the Lewis structure for the compound formed by Li and S, we must first understand the electron configurations of lithium (Li) and sulfur (S). Lithium has one valence electron and sulfur has six valence electrons. Lithium tends to lose one electron to achieve a full outer shell and sulfur tends to gain two electrons to complete its octet.
The Lewis structure for lithium will be '[Li]+' indicating it has lost one electron. For sulfur, '[S]2-' shows it has gained two electrons, each represented by a dot.
Combining these two ions, we get the ionic compound Lithium Sulfide with the formula Li2S, where two lithium ions pair with one sulfide ion to balance the charges. As Li has a +1 charge and S has a -2 charge, two Li+ ions are required to balance one S2- ion.
Predicting the formula of the ionic compound formed between Li+ and S2- ions, we get Li2S.