Final answer:
In chemical formulas for binary ionic compounds where both the metal and nonmetal have oxidation numbers of 1, no subscript numbers are written because the ratio of metal to nonmetal will be 1:1 to balance the charges, resulting in a neutral compound.
Step-by-step explanation:
If we are writing the formula of a compound where both the metal and the nonmetal have oxidation numbers of 1, then according to the conventions of writing chemical formulas for binary ionic compounds, option A is correct: no numbers are written.
Remember, oxidation numbers are used to indicate the general distribution of electrons among the bonded atoms in a compound. When creating chemical formulas, especially for ionic compounds that consist of a metal and a nonmetal, it's important to ensure that the overall charge of the compound is neutral. If both the metal and the nonmetal have oxidation numbers of 1, the ratio of metal to nonmetal would be 1:1 to balance the charges, and no subscript numbers are necessary.
This follows the general guideline that ionic compound formulas are written using the lowest ratio of ions. Since each ion has a charge of +1 or -1, they cancel each other out in a 1:1 ratio, and there's no need to write the number 1 in the formula as subscripts.