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

Which of the following cannot be represented by resonance structures?

Draw the resonating structures of $(A)$ Ozone molecule $(O_3)$ and $(B)$ Nitrate ion $(NO_3^-)$.

$CH_2 = O \leftrightarrow \overset{\oplus}{C}H_2 - \overset{\ominus}{O} \leftrightarrow \overset{\ominus}{C}H_2 - \overset{\oplus}{O}$
Which of these structures is practically not a valid canonical structure for formaldehyde?

How many resonance structures are there for anthracene?

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