Hello!
K⁺ and F⁻ are the more likely to form an ionic bond.
Ionic bonds are the result of the electrostatic attraction between positive and negative ions (charged atoms). Of the listed substances, the ones that are charged are K⁺ and F⁻, so they are the ones that will form ionic bonds. Some ionic substances made from K⁺ include KCl (used in fertilizers) and some ionic substances made from F⁻ include NaF (used in dental therapy).
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