How would you rank these bonds from most ionic to most covalent in character? Br-F, Ca-F. K-F, F-F, Cl-F?

To rank the bonds from most ionic to most covalent in character, we consider the electronegativity difference between the two atoms involved in each bond. The greater the electronegativity difference, the more ionic the bond; the smaller the difference, the more covalent the bond. Here's the ranking:

F-F
Cl-F
Br-F
Ca-F
K-F
Explanation:

F-F has the least electronegativity difference since both atoms are fluorine, so it's the most covalent.
Cl-F has a greater electronegativity difference than F-F, making it more ionic.
Br-F has an even greater electronegativity difference than Cl-F.
Ca-F has an even greater electronegativity difference than Br-F.
K-F has the greatest electronegativity difference among the listed bonds, making it the most ionic.