In general, bonds with an electronegativity difference of 0-0.5 are nonpolar covalent, bonds with an EN difference of 0.5-2.0 are covalent, and anything above 2.0 is considered ionic.
To determine the bond types of the pairs of elements, we will need their EN values. We can subtract their EN values to find their EN difference.
H and Br: 2.96-2.20=0.76 Therefore a bond between H and Br would be moderately polar covalent.
Cl and F: 3.98-3.16=0.82 Therefore this bond is moderately polar covalent.
K and Cl: 3.16-0.82=2.34 Therefore this bond is ionic.
Li and O: 3.44-0.98=2.46 Therefore this bond is ionic.
Br and Br: Because these are the same element, meaning that they have the same EN value, we automatically know that their EN difference would be zero. Therefore, this bond is very covalent.
