Under which of the following conditions is the A—B bond considered to be ionic?

a) when A and B have the same electronegativity

b) when the difference between the electronegativities of the atoms is 1.0

c) when the difference between the electronegativities of the atoms is 1.5

d) when the difference between the electronegativities of the atoms is 2.0

The correct answer is d) when the difference between the electronegativities of the atoms is 2.0. A bond is considered ionic when there is a large difference in electronegativity between the two atoms involved. A difference of 2.0 or more in electronegativity indicates an ionic bond.