Final answer:
The correct chemical formula for potassium nitride, made up of the K+ cation and the N3- anion, is K3N. Three potassium ions are needed to balance the charge of one nitride ion, resulting in a neutral compound.
Step-by-step explanation:
The correct formula for a compound formed from the K+ cation and the N3- anion, referred to as potassium nitride, is not KNO3 as mentioned in the question. The correct formula is K3N. In ionic compounds, the total charge must be neutral. For potassium nitride, three potassium ions (each with a +1 charge) balance out the single nitride ion (with a -3 charge). Therefore, the formula K3N reflects the neutral compound formed by these ions.
Understanding the formulas of ionic compounds and how to combine ions correctly is essential. When forming a compound such as potassium nitride, ensure the total charge is zero by balancing the charges of the cations and anions. Remember that for polyatomic ions, parentheses are used when more than one polyatomic ion is needed, as seen in the case of calcium nitrate, Ca(NO3)2. When determining the correct formula of ionic compounds, use subscripts to indicate the number of each ion present, achieving charge neutrality.