Final answer:
Predicting the ionic compound between potassium and nitrogen involves combining three potassium ions (K+) with one nitride ion (N3-) to form a neutral compound, resulting in the formula K3N with a ratio of 3:1.
Step-by-step explanation:
To predict the formula of a compound formed between the metal potassium and the nonmetal nitrogen, we need to consider the charges that these atoms will most likely have when they form ions. Potassium, being in group 1 of the periodic table, will lose one electron and form a potassium ion with a 1+ charge (K+). Nitrogen, being in group 15 (or 5A) of the periodic table, tends to gain three electrons to achieve a full octet, resulting in a nitride ion with a 3- charge (N3-).
To have a neutral compound, the total positive charge must be equal to the total negative charge. To achieve that, three potassium ions are needed for every one nitride ion. Thus, the formula for the compound is K3N, indicating a potassium to nitrogen ratio of 3:1.