Which of the following is not a valid resonance structure of the others?

Step-by-step solution

To determine which structure is not a valid resonance structure, we need to check if all structures obey the fundamental rules of Lewis structures, particularly the octet rule for period 2 elements like carbon and nitrogen. Let's analyze the valency of the carbon atoms in each structure, specifically the carbon attached to the NH ₂ group (let's call it C1). In structure (A): The C1 atom is bonded to the nitrogen of the NH ₂ group via a single bond. Inside the six-membered ring, there are double bonds drawn on both