Final answer:
F2 is the most covalent due to the absence of electronegativity difference between the two fluorine atoms, whereas LiF is the most ionic due to the large electronegativity difference between lithium and fluorine.
Step-by-step explanation:
The measure of ionic versus covalent character in a bond is determined by the difference in electronegativity between the atoms involved. The larger the electronegativity difference, the more ionic the bond.
F2 is the most covalent because the electronegativity difference between the two Fluorine atoms is zero, signifying a purely covalent bond.
On the other hand, LiF is the most ionic. Lithium (Li) and Fluorine (F) have a large electronegativity difference leading to an ionic bond where electrons are transferred from Li to F.
HF lies between the two as it has a polar covalent character, wherein the electronegativity difference between Hydrogen (H) and Fluorine (F) is significant but not as large as that in LiF.
Learn more about Ionic and Covalent Bonds