First I think it's good to refresh ourselves with the definition of formal charge.
A formal charge is the difference between the number of valence electrons an atom has when it is not bonded to any other atoms and the number it owns when it is bonded.
To do this, there is a formula:
formal charge = number of valence electrons - ( number of lone-pairs + 0.5 number of bonding electrons)
First look at the atom you want to figure out your charge. For this question it's Nitrogen. Nitrogen has 5 valence electrons. If you did not know that already you can look at the periodic table. Ignoring the transition metals in the center of periodic table, you'll find that Nitrogen is on the 5th row, indicating that it has 5 electrons in its outer orbit.
Once you have establish your valence electron number then check it at has any lone pairs. You can tell if there are two dots above your chosen atom. In the first example there isn't one so we will give it a 0 in the formula.
Finally we count the number of bonding electrons. The easiest way to do this is for every sigma bond that connected to the atom in question, it accounts for 2. So in this case, there are 4 sigma bonds attached to nitrogen. Double that and you get 8. There are 8 bonding electrons.
5- (0- (0.5*8) = 1
If we plug all the numbers in we get that the formal charge of this nitrogen is +1 or +
If you follow the same process you should be able to get your formal charge 100 percent of the time!
Here is the work for the reminder charges.
Though it seemingly not used much in the most recent material we've been learning in class, it is still important. Especially when we have been pushing electrons around when breaking, making, and switching bonds around, it's good to check the formal charge to make sure each electron is accounted for.
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