What are ionic bonds usually formed between?
A metal and a non metal or negative polyatomic ion.
Ionic bonds are formed between particles that have a large difference in electronegativity
Metals have a low electronegativity which makes them the ideal cation for the formation of an ionic bond.
Non metals like Chlorine, and sulfur have high electronegativity which when combined with a metal atom with a low electronegativity forms an ionic bond.