Which of the following substances is the most ionic?

Among the following compounds,the one with the highest lattice energy is

The electronic configurations of four elements $L$,$P$,$Q$,and $R$ are given in the brackets:
$L(1s^2, 2s^2 2p^4); Q(1s^2, 2s^2 2p^6, 3s^2 3p^5)$
$P(1s^2, 2s^2 2p^6, 3s^1); R(1s^2, 2s^2 2p^6, 3s^2)$
The formulae of ionic compounds that can be formed between these elements are:

Which of the following is a favourable condition for the formation of an ionic bond?

The lattice energies of $KF$,$KCl$,$KBr$ and $KI$ follow the order:

An atom of an element $A$ has three electrons in its outermost shell and that of $B$ has six electrons in the outermost shell. The formula of the compound between these two will be