The question asks to identify the compound with the strongest ionic character. My answer was KBr, but the correct answer is CsCl.

This is my reasoning:
1) We learned in class that ionic charge and atom size influence ionic character. Increased ionic charge difference between elements increases ionic character and decreased atomic size increases atomic character.
2) Since both KBr and CsCl have the same ionic charge differences, the smaller elements (ie. KBr) will have more ionic character.

The reasoning on AAMC:
1) There is an electronegativity table of certain elements. Since electronegativity decreases down a group, we should be able to predict that Cs has electronegativity 0.8 or less.
2) There is a bigger difference in electronegativity in CsCl.

I am puzzled about this question because the electronegativity explanation seems to suggest that ionic character increases with increased atomic size (since atomic size increases down a group, whereas electronegativity decreases down a group). However, this contradicts the fact we learned in class that ionic character increases with decreased atomic size because increased atomic radius.