Which of the following would be the best name for MgCl2? magnesium chlorine magnesium chloride magnesium dichloride monomagnesium dichloride

It would be magnesium chloride.

Chlorine is a wrong name for Cl.

Dichloride doesn't work, even though Cl2 is 2 chloride, but according to some laws of nomenclature, saying dichloride isn't necessary so we don't say it.

And monomagnesium isn't right for the same reason as above.