Question

I have no idea how to do this, and i have a test on it tomorrow.

Answer 1

b. Hydrogen has one valence, Carbon has 4, nitrogen has 5, and oxygen has 6. In the b diagram we see that hydrogen has a formal charge of 0 carbon has a formal charge of 0 as well, nitrogen has a formal charge of 1 and oxygen has a formal charge of minus one. Here is how I did that. First you need to know the valence on each. Valence will always be the same. Let me know if you don't understand how to find valence. Next you find the number of electrons that are non bonding plus the amount that are. An easy way to do it is any line equals one and any dot equals one. For nitrogen you would say there are 0 non bonding and 4 bonded because there are 4 lines. For oxygen there are 6 not bonded and 1 bonding .To find formal charge just subtract the valence from the sum of non bonded and bonded electrons. For Nitrogen we get 5 for valence and 4 for the sum. That equals a 1 formal charge. This makes sense becuase nitrogen normally has 5 electrons but in this case it only has 4 so we put a +1 charge on it to show that. Oxygen has 6 valence and 7 for the sum so we get a negative one. which also makes sense becuase this means in that diagram oxygen has one more electron on it than in it's ground state. If you have a choice between two configurations that are similar always put the negative one formal charge on the more electronegative element. The difference between B and C is that the negative charge is on the carbon in C where it's on the oxygen in B. B is more likely to happen than C due to Oxygen being more electronegative. Hope that helps