Question: which bonds are most ionic?
Answer: K-F would be the most ionic because K has an electronegativity of 0.82 and F has an electronegativity of 3.98.
Ca-F would be next. Ca has an electronegativity of 1.00.
Br-F. ... 
Cl-F. ... 
F-F is the most covalent because the electronegativity values are the same so the difference would be zero.