Which one of the following metal complexes is most stable?

The ionic radii of F^$$-$$ and O^2$$-$$ respectively are 1.33$$\mathop A\limits^o $$ and 1.4$$\mathop A\limits^o $$, while the covalent radius of N is 0.74$$\mathop A\limits^o $$.

The correct statement for the ionic radius of N^3$$-$$ from the following is :

The correct decreasing order of densities of the following compounds is :

Consider the above reaction, the product "P" is :