Answer:
a. Cl and Al.
Explanation:
Hello,
In this case, considering that the bond's nature is defined by the result of the difference between the electronegativities of the elements constituting the compound, the pair of atoms that do not exhibit an ionic bond is Cl and Al since such difference turns out:
\(\Delta E=E_{Cl}-E_{Al}=3.16-1.61=1.55\)
Whose result is not eligible for ionic bond but polar covalent bond as long as ionic bonds are formed when the difference is higher than roughly 1.7.
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