What part of the chemical formula tells you how many of each ion you have?

Question

Explain please

Answer 1

To write an ionic formula take the ion charge for each ion and crisscross to be the subscript of the other ion. Example Mg⁺² and F^-1 crisscross to become MgF₂ ( dont include the 1 in a chemical formula). This subscript tells us that for every Mg ion there are 2 F ions.