What is the $O-O$ bond length in the ozone $(O_3)$ molecule (in $pm$)?

What points should be kept in mind while drawing resonance structures?

The correct order of sulphur-oxygen bond order in $SO_3$,$S_2O_3^{2-}$,and $SO_4^{2-}$ is:

$H - N\mathop { - - - }\limits^{(I)} N\mathop { - - - }\limits^{(II)} N$
In hydrogen azide,the bond orders of bonds $(I)$ and $(II)$ are . . . . . .

In the $HCOO^{-}$ anion,the two carbon-oxygen bonds are found to be of equal length. What is the reason for this?

Which of the following compounds will not exist as a resonance hybrid? Give a reason for your answer.
$(a)$ $CH_3OH$
$(b)$ $RCONH_2$
$(c)$ $CH_3CH=CHCH_2NH_2$