What are the important characteristics of ionic compounds?

Which one is most ionic? Explain with reason.

${\mathrm{MgCl}}_{2 }, {\mathrm{CaCl}}_2, \mathrm{CaO}$ and ${\mathrm{PCl}}_5$.

 Which of the following species have same shape?

 ${\mathrm{NO}}_2^{+}, {\mathrm{NO}}_2^{-}, {\mathrm{CO}}_2$ and ${\mathrm{O}}_3$. 

Which bond do you expect to be stronger in the following case and why?

$\mathrm{H}-\mathrm{H}, \mathrm{Cl}-\mathrm{Cl}$.

Which bond do you expect to be stronger in the following case and why?

${\mathrm{O}}_2, {\mathrm{N}}_2$.

Which bond do you expect to be stronger in the following case and why?

$\mathrm{F}-\mathrm{F}, \mathrm{Cl}-\mathrm{Cl}$.