The lattice energy of an ionic compound depends on which of the following?

Two elements have electronegativities of $1.2$ and $3.0$. The bond formed between them would be:

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:

In the crystals of which of the following ionic compounds would you expect maximum distance between the centres of cations and anions?

Out of the following,which compound will have electrovalent bonding?

Amongst sodium halides $(NaF, NaCl, NaBr, NaI)$,$NaF$ has the highest melting point because of: