Formal charge

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Dakota Walker 1L
Posts: 58
Joined: Wed Sep 18, 2019 12:17 am

Formal charge

Postby Dakota Walker 1L » Tue Oct 29, 2019 10:17 pm

When drawing lewis structures do we need to calculate all formal charge options in order to decide how the structure should be drawn? Or can you just draw it based on electrons and guess on the double bond.

Justin Sarquiz 2F
Posts: 106
Joined: Fri Aug 30, 2019 12:15 am

Re: Formal charge

Postby Justin Sarquiz 2F » Tue Oct 29, 2019 10:54 pm

You should calculate the formal charges in order to see which structure has the lowest energy. Once you get the hang of it, calculating the formal charge only takes a couple of seconds, so it will not take up that much of your time.

Abigail Sanders 1E
Posts: 112
Joined: Wed Sep 11, 2019 12:16 am

Re: Formal charge

Postby Abigail Sanders 1E » Wed Oct 30, 2019 12:36 am

As was previously stated, formal charge does not always have to be calculated to find the lowest energy structure, however, it often aids in deciding which structure has formal charges closest to 0 for the central and outward atoms.

aphung1E
Posts: 101
Joined: Sat Aug 24, 2019 12:15 am

Re: Formal charge

Postby aphung1E » Wed Oct 30, 2019 1:01 am

Can someone explain how to find the lone pair electrons when trying to find the formal charge?

aphung1E
Posts: 101
Joined: Sat Aug 24, 2019 12:15 am

Re: Formal charge

Postby aphung1E » Wed Oct 30, 2019 1:04 am

While trying to find the formal charge, how do you find the shared electrons?

Maya Pakulski 1D
Posts: 105
Joined: Thu Jul 11, 2019 12:17 am

Re: Formal charge

Postby Maya Pakulski 1D » Wed Oct 30, 2019 9:28 am

aphung1G wrote:Can someone explain how to find the lone pair electrons when trying to find the formal charge?

When finding lone pair electrons you just count the pairs of electrons that are not bonded to another element. For example in the Lewis structure for water, the O has two bonds and two lone pairs because it has four unbonded electrons.

Veronica_Lubera_2A
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Joined: Sat Sep 14, 2019 12:16 am
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Re: Formal charge

Postby Veronica_Lubera_2A » Wed Oct 30, 2019 9:33 am

When a question asks for the most stable resonance structure, you have to draw the different lewis dot structures (only switching the placement of bonds) and calculate formal charges. The ones closest or equal to 0 will be the most stable and therefore be the answer.

Brynne Burrows 3K
Posts: 52
Joined: Thu Jul 25, 2019 12:16 am

Re: Formal charge

Postby Brynne Burrows 3K » Wed Oct 30, 2019 10:14 am

aphung1G wrote:Can someone explain how to find the lone pair electrons when trying to find the formal charge?

Whichever pairs of electrons that cannot be replaced by a bond when the Lewis structure is drawn out can be counted as a lone pair. It helps to see the picture in order to determine lone pair electrons.

Sara Richmond 2K
Posts: 110
Joined: Fri Aug 30, 2019 12:16 am

Re: Formal charge

Postby Sara Richmond 2K » Wed Oct 30, 2019 2:17 pm

AN easy way to calculate formal charge of an atom is:

# of valence electrons for that element- number of dots-number of lines=formal charge

BCaballero_4F
Posts: 94
Joined: Wed Nov 14, 2018 12:22 am

Re: Formal charge

Postby BCaballero_4F » Wed Oct 30, 2019 6:25 pm

I would recommend counting the formal charge so you have the most similar structure to what the real structure looks like.


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