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Yes, it is desirable for molecules to have the lowest energy lewis structure possible so that it can have the most stable structure. The lower the formal charge for the molecule overall and also for the individual atoms themselves, the more stable the structure.
victoria1l wrote:Instead of calculating the formal charge, could one simply make sure that all the atoms have the correct number of valence electrons ? or would this not work all the time?
I believe that method would not work all of the time because some elements violate the octet rule. For instance, phosphorous holds up to 10 electrons and sulfur holds up to 12 electrons. (There are more exceptions than those I just mentioned.)
Because you always want the lowest formal charge possible in order to have the most stable Lewis Structure. I heard from my TA that it is possible you will have to calculate formal charges for points on either Test 3 or the final.
If having a formal charge of 0 means that an atom is most stable, then why do atoms like chlorine tend to have a negative charge when isolated (ie Cl-)?
I'm not entirely sure I'm correct here, but I think the reason we usually write Cl as Cl- doesn't have to do with formal charge so much as the fact that Chlorine has seven valence electrons and therefore needs an additional electron to achieve a stable octet. Pure Chlorine with seven valence electrons (simply Cl) doesn't exist in nature because it is unstable. Instead, Chlorine is either bonded with another element (NaCl), itself (Cl2) or it exists as an anion (Cl-). It's the same reason Na is often denoted instead as Na+, since sodium exists in the world not as the unstable Na, but the cation Na+ or in a bonded molecule. It all has to do with ensuring that the version of Chlorine or Sodium we are dealing with is stable.
Hope this can be helpful!
As Professor Lavelle has explained, you want to have the lewis structure in the most stable form. It's important to know what each individual elements charge is because it determines where the element should be placed in the structure.
If you had a molecule with three different lewis structures (resonance) and they had formal charges each with multiple zeros, would you pick the lewis structure with the most zeros/lowest formal charge to be the most stable lewis structure of that molecule?
Because of resonance, you can create various different structures of the same compound. But the version with the lowest formal charge is the most suitable. For this reason, we calculate formal charge.
kellyzhang1210 wrote:why is the element most stable when its formal charge is 0?
When the formal charge of an element is 0, it's in the neutral state, which means that the amount of electrons is kind of "balanced" so that's why there is less instability.
Formal charge has to be considered when drawing lewis structures as it will help you figure out if there is a double bond or not while trying to figure out the most stable form of the compound.
Moris 1H wrote:Why us calculating formal charge important for every Lewis Structure?
Calculating the formal charge is important because when FC=0 that is when your structure is the most stable. That way you can verify that your structure is correct in terms of your placement of electrons.
Formal charges also allow you to compare different possible lewis structures for the same molecule. For example, if the oxygen atoms in one lewis structure have positive formal charges and negative formal charges in another, the second lewis structure is probably preferable (assuming that other factors are taken into account) since oxygen is more electronegative than, say, carbon or nitrogen, and would rather have a negative formal charge than the aforementioned elements.
Compounds naturally want to be at their most stable form. By using formal charges and equalling them to 0, we are better able to find what is ACTUALLY the most stable structure of the compound so that we know what the structure of the compound actually is in nature.
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