Finding Most Stable Structure


Moderators: Chem_Mod, Chem_Admin

Angelo Mapalo 4E
Posts: 50
Joined: Sat Aug 24, 2019 12:18 am

Finding Most Stable Structure

Postby Angelo Mapalo 4E » Sun Oct 27, 2019 9:20 pm

How do we determine which structure is the most stable with formal charge?

AndreiRekesh1I
Posts: 52
Joined: Fri Aug 30, 2019 12:15 am

Re: Finding Most Stable Structure

Postby AndreiRekesh1I » Sun Oct 27, 2019 9:21 pm

When formal charge on atoms (usually the center atom is most important) is zero, then that configuration is the most stable.

Nikki Razal 1L
Posts: 116
Joined: Fri Aug 30, 2019 12:17 am
Been upvoted: 1 time

Re: Finding Most Stable Structure

Postby Nikki Razal 1L » Sun Oct 27, 2019 9:39 pm

The most stable compounds typically have an overall total charge of zero (the exception would be if the compound or element is an anion or cation, that is, if they have an overall charge other than zero). And just a quick note, formal charge = # of valence electrons an atom has - (# bonds + lone pair electrons), or # of valence electrons an atom has - (# of lone pair electrons + # of shared electrons/2)

John Liang 2I
Posts: 102
Joined: Fri Aug 30, 2019 12:18 am

Re: Finding Most Stable Structure

Postby John Liang 2I » Sun Oct 27, 2019 10:08 pm

Remember that when calculating formal charge for lds of ions, the sum of the formal charges must add up to the overall ion's charge.

ZevMarx-Kahn3C
Posts: 52
Joined: Sat Aug 17, 2019 12:17 am

Re: Finding Most Stable Structure

Postby ZevMarx-Kahn3C » Sun Oct 27, 2019 11:45 pm

How do we know when we're dealing with the most stable version? Are naturally occurring molecules always the most stable versions of themselves?

Sam McNeill 1E
Posts: 110
Joined: Sat Aug 24, 2019 12:17 am

Re: Finding Most Stable Structure

Postby Sam McNeill 1E » Mon Oct 28, 2019 11:16 am

You know you are dealing with the most stable version when the Formal Charges are closest to zero. Try to find the different structure for the naturally occurring molecule, and whichever is closest to zero is the most stable.

Sean Cheah 1E
Posts: 105
Joined: Wed Sep 18, 2019 12:20 am

Re: Finding Most Stable Structure

Postby Sean Cheah 1E » Mon Oct 28, 2019 12:30 pm

In cases where it is impossible to entirely eliminate the formal charge on each atom, the most stable structure will have the negative formal charges on the more electronegative atoms and the positive formal charges on the less electronegative atoms.

005162902
Posts: 102
Joined: Wed Sep 18, 2019 12:15 am

Re: Finding Most Stable Structure

Postby 005162902 » Mon Oct 28, 2019 12:34 pm

Using the equation given in class, you can find the formal charge of a molecule. When the FC equation equals zero, you have reached the most stable form of the compound. If it does not equal zero, you know some modifications can be made to the electrons or bonds in order to reach a FC of zero and have a more stable compound.

Clara Cho 2K
Posts: 103
Joined: Wed Sep 18, 2019 12:18 am

Re: Finding Most Stable Structure

Postby Clara Cho 2K » Mon Oct 28, 2019 12:50 pm

How do you know which atom can hold more of the negative charge?

Sean Cheah 1E
Posts: 105
Joined: Wed Sep 18, 2019 12:20 am

Re: Finding Most Stable Structure

Postby Sean Cheah 1E » Mon Oct 28, 2019 1:02 pm

Clara Cho wrote:How do you know which atom can hold more of the negative charge?

To maximize the stability of your structure, any remaining negative formal charge should be preferably assigned to the more electronegative elements first. I'm sure Lavelle will not expect us to memorize the electronegativities for all the various elements, so while there are several exceptions, just remember that electronegativity generally increases going left to right across a period and decreases going down a group. As an example, in the sulfate ion (SO4 2-), one would ideally place the negative formal charges on the oxygen atoms before the sulfur atom, as oxygen has a higher electronegativity.


Return to “Formal Charge and Oxidation Numbers”

Who is online

Users browsing this forum: No registered users and 1 guest