$HNO _{3}+ P _{4} O _{10} \longrightarrow \underline{ N _{2} O _{5}}+ H _{3} PO _{4}$ Structure of $N _{2} O _{5}$
It is diamagnetic and does not contain $N-N$ bond.
$Na + N _{2} O _{5} \longrightarrow NaNO _{3}+ \underset{\text{brown gas}}{NO _{2}} \uparrow$