I have a test tomorrow and I don't really understand how to do formal charge and I've been looking at it and it just isn't clicking. Thank you for your help.
Count the electrons around the atom. If the electron(s) is/are shared with another atom, half goes to one atom and half to the other. Subtract the number the atom has (with the charge) from what it should have (with the charge) and that is the formal charge. These things are hard to do on the Internet but here is an example.
:N:::N:O: plus .. above O and .. below O. Count them and you should have 16 electrons.
For the left N, the first two are not shared so that counts as two. the next six are shared so that counts as three (1/2 of 6). That gives the first N five electrons. It had 5 to start with so the FC is 0 [-5-(-5)=0]. The second N has three on the left (again, 1/2 of 6) and a shared pair on the right (which counts as one electron). That adds to 4, it had 5 to begin with so the FC is +1 [-4 -(-5)=+1]. For oxygen, there are six unshared and one pair shared (which counts as one) and O has six to start with so we have -7 -(-6)=-1
Please explain where you have trouble if you are still confused.
Formal charge is a way to assign charges to atoms in a molecule in order to determine the most stable electron distribution. To calculate formal charge, you can follow these steps:
1. Count the electrons around the atom: Look at the Lewis structure or molecular formula of the molecule and count the total number of valence electrons around the atom in question.
2. Assign bonding electrons: If the electron(s) is/are shared with another atom, divide the number of shared electrons equally between the bonded atoms. Each shared pair of electrons counts as one electron for each atom. Subtract the number of shared electrons from the total valence electrons count.
3. Assign non-bonding electrons: If the atom has any unshared or non-bonding electrons, count them individually.
4. Calculate formal charge: Subtract the sum of the assigned electrons from the original valence electron count of the atom. The result is the formal charge.
Here's an example using the molecule you provided, :N:::N:O:
First, count the valence electrons: In this case, there are 16 valence electrons.
For the left nitrogen (N), there are two unshared electrons and three shared electrons (1/2 of 6 shared electrons), which adds up to 5. Since nitrogen has 5 valence electrons, the formal charge is 0 (5 - 5 = 0).
For the right nitrogen (N), there are three shared electrons (1/2 of 6 shared electrons) and one unshared electron, which adds up to 4. Since nitrogen has 5 valence electrons, the formal charge is +1 (5 - 4 = +1).
For oxygen (O), there are six unshared electrons and one shared pair of electrons, which counts as one electron. Since oxygen has 6 valence electrons, the formal charge is -1 (6 - 7 = -1).
By calculating the formal charges, we can determine the electron distribution within the molecule.
If you're still confused about any specific step or aspect of formal charge, feel free to ask for further clarification.