$CH_2=CH-CH=CH-NH_3^+$ $(I)$
$^+CH_2-CH=CH-CH=NH_3^+$ $(II)$
$^+CH_2-CH=CH-CH=NH_3$ $(III)$
Which of these structures is not a valid canonical structure?

All bond lengths are identical in :-

Write the resonance structures of $CO_3^{2-}$ and $HCO_3^{-}$.

Which of the two structures $A$ $(CH_3COOH)$ and $B$ $(CH_3COO^-)$ given below is more stabilised by resonance? Explain.

Examine the following resonating structures of formic acid for their individual stability and then answer the question given below.
$(I)$ $H-COOH$
$(II)$ $H-C(OH)=O^+$
$(III)$ $H-C^+(OH)-O^-$
$(IV)$ $H-C^-(OH)-O^+$
Which of the following arrangements gives the correct order of decreasing stability of the above-mentioned resonance contributors?

Among the structures given below,which one is not a correct resonance structure of $N_3^-$?