Which Chemical Species Has the Lowest Energy Based on Formal Charge?

In summary, the speaker is trying to determine the most stable structure among three chemical species with a formal charge of -3. They mention that the first one is the most logical choice due to the presence of d-orbitals in As and oxygen's tendency to form double bonds. They also mention two rules for determining the most stable structure, with the first one having the lowest sum of formal charges and the second one having the largest negative formal charge on the most electronegative element. However, the speaker believes that there may be a mistake in the provided rules and suggests that the most stable structure may be the one in the center.
  • #1
omni
192
1
i found the Formal charge of 3 Chemical species, now i asked to decide which one יhave the most low energy.

how can i know it, all have -3 at the sum.

i need help in this section.thanks.
 

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  • #2
What do you mean by 'the lowest energy'? I can tell you which one is the most stable: the first one. Since As has d-orbitals, it is able to form more than 4 bonds. Combine this with the fact that oxygen tends to form double bonds, and it is readily seen that the first is the logical choice.

The most stable structure is the one with:
a) the lowest sum when the absolute values of the formal charges are added
b) the largest negative formal charge on the most electronegative element (when 2 or more
structures have the same lowest sum)
 

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  • #3
hi thank you very much.
you really helped me :)

but i think you have a mistake if we work with the rules from what you given and since o is more electronegative than As so if we follow after rule b the most stable structure is the one in the center.
 
Last edited:

1. What is formal charge?

Formal charge is a concept used in chemistry to determine the distribution of electrons in a molecule. It is calculated by assigning each atom in the molecule a charge based on the number of valence electrons it possesses and the number of electrons it shares in covalent bonds.

2. How is formal charge calculated?

Formal charge is calculated by subtracting the number of non-bonding electrons and half of the bonding electrons from the total number of valence electrons of an atom. The sum of all formal charges in a molecule should equal the overall charge of the molecule.

3. What is the significance of formal charge in molecules?

Formal charge helps to determine the most stable arrangement of electrons in a molecule. It also provides insight into the reactivity and properties of molecules. In some cases, minimizing formal charge can lead to more stable and low energy structures.

4. How does formal charge affect the energy of a molecule?

Generally, a molecule with lower formal charges will have lower energy because the electrons are more evenly distributed. However, there are exceptions where the formal charge does not accurately reflect the true electronic distribution and the energy of the molecule may be affected by other factors.

5. Can formal charge be used to predict the geometry of a molecule?

No, formal charge alone cannot be used to predict the geometry of a molecule. The shape of a molecule is determined by a combination of factors, including the number of bonding and non-bonding electrons, the types of bonds present, and the repulsion between electron pairs. Formal charge can provide some insight, but it should not be the sole factor in determining molecular geometry.

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