Question

The answer is B but why and how we can solve such problem?

Answer 1

Answer:

$\text{CsF}$

Explanation:

Here, we want to get the most ionic fluoride

Cs is a group 1 element, same as sodium

However, we know that electropositivity increases down the group while electronegativity decreases down the group

Also, electropositivity decreases across the period. It is expected that a group 1 element will be more electropositive than a group 3 element.

Thus, we are having a bond between a very electropositive metal and a very electronegative non-metal. That is why we have CsF (it is the strongest and most electropositive atom in the options listed) as the molecule with the strongest ionic bond on the list