Add formal charges to each resonance form of hcno below. based on the formal charges you added above, which structure is favored?

The second structure is the most stable of all three.

Explanation:

The Formal Charge in the different resonance structures of HCNO is,

Where,

FC- Formal charge

V- Valence Electron

N- Non-bonding Electron

B- Number of bonds

So,  Formal charge In the atoms of first resonance structure is

H = 1-0+1=0

C = 4 -4+2 = -2

N = 5 - 0+4 = 1

O = 6 - 2 + 3 = 1

Formal charge In the atoms of Second resonance structure is

H = 1-0+1 = 0

C = 4 - 0 + 4 =0

N = 5 - 0 + 4 = 1

O = 6 - 6+1 = -1

Formal charge In the atoms of Third resonance structure is

H = 1-0 + 1 = 0

C = 4 - 2 +3 = -1

N = 5 - 0 + 4 = 1

O = 6 - 4 +2 = 0  

To Figure out the most stable resonance structure we have to keep two things in mind:

1) The stable molecular structure tend to have the least number of charged atom.

2) In a stable molecular structure the negative charge is present in the more electronegative atom.

Here decreasing order of electronegativity is,

 N > O > C > H

From the Explanation above, the second structure (B) follows both points

Therefore, The second structure is the most stable of all three.

For more details, you can refer to the link:

link

i believe the answer is a.

i think its 5049.

i hope this !