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Within a Lewis Structure, will the formal charge of an atom of that element always be the same? This will always be the same, regardless of different bond types, right? For Example in CO3 with a -2 charge, all of the oxygen atoms will have a formal charge of -1, regardless of one of the oxygens having a double bond instead of a single bond. Is this the right idea, or is the formal charge of oxygen in this case just a coincidence?
Each atom gets its own formal charge, even if it is the same element as another one in the molecule. In CO3^2-, all of the oxygen atoms have an FC of -1, but that is a coincidence. An example of two oxygen atoms having a different FC in the same molecule would be nitrite, NO2-, where the oxygen with a single bond has an FC of -1 and the oxygen with a double bond has an FC of 0.
Adding onto what the previous person stated, formal charge refers to the number of valence minus the number of bonds divided by 2 and the number of nonbonding electrons (the dots). Each atom gets its individual charge according to the number of bonds there are and valence electrons there are. Therefore, it does differ depending on the bond type (double or single).
No, as each reply has stated, each atom has its own formal charge. Even though there could be 2 of the same element in a lewis structure, their formal charges are dependent on the amount of bonds and lone pairs they are connected to. This could result in 2 atoms of the same element having different formal charges.
The formal charge is different for each atom in each molecule. In additional, the formal charge can change based on the number of bonds. So no, oxygen will not always have a formal charge of -1. It could in fact have a formal charge of 0. For example in NO3-, there is an oxygen with a double bond with Nitrogen and the two other oxygens have a single bond with nitrogen. Therefore, even within the same molecule, these oxygens have different formal charge. The double bond oxygen would have 4 lone pair electrons and 4 paired electrons. This would give the double bond oxygen a formal charge of 6-4-(4/2)=0 and give the single bond oxygen 6-6-2/2=-1
The formal charge of an element can vary, even within the same molecule. A great example of this is resonance structures, such as nitrite (NO2^-). In the lewis structure of nitrite, one of the oxygen has 3 lone pairs and a single bond with nitrogen, giving it a formal charge of -1. The other oxygen has 2 lone pairs and a double bond of nitrogen, giving it a formal charge of 0. Depending on the number of lone pairs and bonded pairs of electrons the element has, the formal charge can change.
The formal charge can be different in some cases. For example, in Dr. Lavelle's lecture 14, he adds 2 more covalent bonds to the central atom S in SO4(2-). Adding more covalent bonds to the central atom made the formal charge of 2 Oxygen atoms 0 while the other 2 remained -1.
The formal charge of the same element can differ based on the amount of bonds it has and the number of valence electrons as those numbers would result in varying charges when plugged into the formal charge formula. To be safe try to find the formal charge of all atoms of the element, even if they are the same, to see if you can come up with the same overall charge of the molecule given.
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