Lowest Energy Lewis Structure

[Cecilia Cisneros 1F]

Would the lowest energy structure be the one where the negative FC is on the most electronegative atom? For example the structure of NO2. It could be drawn two ways with a +1 charge on central N atom and a -1 on the O OR a +1 charge on the central N atom and a -1 charge on the other N atom. Which would be the lowest energy Lewis Structure?

[AustinMcBrideDis3L]

Yes, if you are unable to attain a structure with 0 formal charge on all the atoms you generally should draw the lewis structure in a formation that puts negative formal charges on the more electronegative atoms (typically the non-central atoms).

[Neha Gupta 2A]

Adding on to this, since O is very electronegative does that mean it shouldn't be the central atom in lewis structures?

[Madeline Louie 1I]

The lowest energy lewis structure will have the negative formal charge on the most electronegative atom and the positive formal charge on the least electronegative atom. The closer the formal charge is to zero the better!

[Madeline Louie 1I]

Adding on to this, since O is very electronegative does that mean it shouldn't be the central atom in lewis structures?

Neha, the least electronegative atom is in the middle, and since nitrogen is less electronegative, it is the center atom.

[Sahaj Patel Lec3DisK]

Always strive to have the most zeros throughout your molecule in terms of formal charges. You should always try to make your central atom have a formal charge of zero as well.

[Andre Fabian 1F]

The lowest energy structure would be the one where the most atoms have a FC of 0 (or the lowest FC). For example, while comparing two resonance structures of the same species, if one has atoms with formal charges of +1, -2, +1 while the other has the formal charges of +1, -1, 0, the latter would have the lowest energy structure.


Hope this helps!

[Carly_Lipschitz_3H]

The lowest energy structure would be the lewis structure with the FC closest to zero. This includes having as many elements with a FC of zero as possible. Usually, it's best to put the charges on the most electronegative atom like you said. When there has to be a formal charge that does not equal zero, to get the most stable structure there should be negative formal charges on the more electronegative atoms and positive formal charges on the less electronegative atoms in the structure.

[Joshua Eidam 2A]

Adding on to this, since O is very electronegative does that mean it shouldn't be the central atom in lewis structures?

Neha, the least electronegative atom is in the middle, and since nitrogen is less electronegative, it is the center atom.

This is not to say though that oxygen can't be the central atom, we see this to be the case for H2O, but like previously stated, the least electronegative is usually in the middle, and since O is very electronegative, it frequently is not the central atom.