Final answer:
One K+ ion and one F- ion combine to form the neutral ionic compound KF, which is called potassium fluoride.
Step-by-step explanation:
To determine the number of K+ and F− ions needed to form a neutral ionic compound, we look at the charges on the ions. Potassium ions (K+) have a charge of +1, whereas fluoride ions (F−) have a charge of -1. To achieve a neutral compound, the total positive charge must balance the total negative charge. Since both ions have charges of the same magnitude but opposite signs, we need one potassium ion to balance one fluoride ion. Therefore, the formula for the neutral ionic compound formed by these ions is KF, which is known as potassium fluoride.