1. Identify the nonmetal and the Group A metal involved.
2. Determine the charges of the nonmetal and the Group A metal ions.
3. Use the criss-cross method to determine the empirical formula of the compound.
For example, consider the reaction between sodium (a Group A metal) and chlorine (a nonmetal).
1. Sodium has a charge of +1, while chlorine has a charge of -1.
2. To balance the charges, we need one sodium atom for every one chlorine atom.
3. The empirical formula of the compound formed is therefore NaCl.
This same approach can be used to predict the correct formula for any combination reaction between a nonmetal and a Group A metal.
