The Crisscross method is a method of finding out the chemical formula of a metal and non-metal that combine to form an ionic bond.
To use this method, the absolute value of the oxidation number of the first ion is used as the subscript of the second, and vice versa. The subscripts are then reduced by the greatest common factor. For instance, to find the formula for magnesium oxide
The first word is the metal, which retains its name. The second word is the non-metal, which retains its element prefix and add ...IDE as its suffix. The subscript number of an element doesn't affect the name
eg: Al3 S2-
Which then becomes Aluminum Sulfide