Final answer:
The formula for sodium nitride, which is not a commonly referenced compound, is Na3N. If the intended compound is sodium nitrate, a more common substance, the formula would be NaNO3.
Step-by-step explanation:
The correct formula for sodium nitride would be Na3N. However, it seems there might be confusion in the question provided, as sodium nitride is not a common compound. Instead, sodium nitrate, NaNO3, is more well-known. To write the formula for an ionic compound such as sodium nitrate, we would first note the charges of the sodium cation (Na+) and the nitrate anion (NO3−). Since the sodium ion has a +1 charge and the nitrate ion has a -1 charge, one of each will balance the charges and give us NaNO3 as the formula for sodium nitrate.