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10.7 Lewis Structures of Molecular Compounds and -- Part 1
When calculating the number of electrons for the Lewis structure, pay special attention to the charge of the ion.
Add one electron for each negative charge and subtract one electron for each positive charge.
Write the structure of the skeleton.
The H N H nitrogen atom should be in the central position.
The total number of electrons for the Lewis structure is calculated by summing the number of electrons for each atom and subtracting the number of electrons for each atom.
Add 1 e- to account for the charge of ion.
We can write more than one Lewis structure for some molecules.
Write a Lewis structure for O3.
The bonds in the O3 molecule are equivalent and each is intermediate in strength and length between a double bond and single bond.
The structure of a resonance hybrid is intermediate between the two resonance structures.
Individual resonance structures do not exist and are merely a way to describe the actual structure, which is the hybrid structure.
The structure of ozone has two equivalent bonds and a bent geometry.
The structure of a resonance hybrid is intermediate between that of the contributing resonance structures and the offspring of two different dog breeds.
The concept of resonance is an adaptation of the Lewis model.
For reasons that are beyond the scope of this book, the delocalization of electrons lowers their energy.
In order to more accurately reflect the delocalization of electrons, Resonance depicts two or more structures with the electrons in different places.
The average between the resonance structures is more spread out than in any of the resonance structures.
It's important that resonance stabilization contributes to the stability of the molecule.
The NO 3 ion requires a Lewis structure.
Write the structure of the skeleton.
It was put in the central position.
To calculate the total number of electrons for the Lewis structure, add the number of valence e- in N and O to the number of electrons for each atom.
Add 1 e- to the account.
There aren't enough electrons to complete the octet on the central atom.
The actual space-filling model of NO 3 is shown here.
The NO 2 ion requires a Lewis structure.
The structures that contributed to the resonance hybrid have been the same as the Lewis structures.
The true structure is an average of the resonance structures.
We can write resonance structures that are not equivalent.
One resonance structure may be better than another for certain reasons.
The better resonance structure contributes more to the true structure than the average resonance structure.
The effects of electronegativity are completely ignored.
The hydrogen atom has a slight positive charge and the fluorine atom has a slight negative charge.
The formal charge on any atom can be calculated as the difference between the number of electrons in the atom and the number of electrons in a Lewis structure.
The concept of formal charge can help us distinguish between competing structures.
The neutral molecule must have zero formal charges.
The charge of the ion must be equal to the sum of all formal charges.
Smaller formal charges on individual atoms are better than larger ones.
When formal charge can't be avoided, negative formal charge should reside on the most negative atom.
We can use formal charge to determine which of the competing structures is the most stable.
Both structures satisfy the octet rule.
The structure's formal charge is calculated below it.
The formal charges for each of these structures are zero.
Both structure B and structure A have formal charges on the N and C atom.
The negative formal charge is not on the most negative element in structure B.
The better structure is structure A.
Since atoms in the middle of a molecule tend to have more bonding electrons and less nonbonding electrons, they also have more positive formal charges.
HNC is more stable than HCN because it has the least electron negative atom in the central.
The formal charges for each structure are -1, which is what they should be.
A and B have the least formal charges and are preferred over C. The biggest contribution to the resonance forms of the cyanate ion will be made by structure A.
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