Which of the following is not correct for ionic crystals?

The correct statement for the molecule,$CsI_3$ is:

An electrovalent compound is made up of

In which of the following compounds is the ratio of the size of the anion to the cation the smallest?

The electronic configurations of elements are $A = 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2$ and $B = 1s^2 2s^2 2p^6 3s^2 3p^5$. Which of the following is the formula of the ionic compound that could be formed between these two elements $A$ and $B$?

Between $HF$,$HCl$,$HBr$ and $HI$,$HF$ has the highest ionic character because