Can someone explain, in detail, how an ionic bond is formed between Cl2 and Ca?

In an ionic bond, 2 or more ions share electrons to get an octet in their second ring. The cation (calcium) and anion (chlorine) will bond together as CaCl2. Calcium has 2 more electrons than it needs for a noble gas configuration, so it gives up one electron a piece to each chlorine. The two bond because of electrostatic forces that result from the new electron pairs. They bond because they are more stable together. Hope this helps.