Chemistry Ionic Bonds. Which is the strongest?

[name_ask17]

Homework Statement

Which has the strongest ionic bond?
Cs2Se
AlN
CaI2
Kbr

Homework Equations

Look at electronegativities

The Attempt at a Solution

I looked at electronegativities and found the differences.
The largest difference was KBr. But apparently, that was wrong. See EN differences below.

Cs2Se: 1.6
AlN: 1.5
CaI2: 1.5
KBr: 1.9

Ionic bond strength increases with increasing change in EN, correct?
What am I doing wrong?
Please advise if you can.
Thanks in advance.

 

[name_ask17]

Oh wait. I figured it out. You look at charges, not the EN difference for this part. So, AlN would be the answer.