Formal Charge

[Paula Dowdell 1F]

When do you know that your lewis structure has a good formal charge?

[Andrea Grigsby 1I]

when the formal charge = 0

[Gobinder Pandher 3J]

The formal charge does not always need to equal 0 for the Lewis Structure to be favorable. If the compound has an overall charge (for example, OH^-) then the overall formal charge between all elements will be -1. What makes a Lewis Structure favorable is its ability to have the lowest formal charge numbers between all elements. To clarify, the closer the Formal Charges for each element are to zero, the more likely that Lewis Structure will be favored. I hope this helps!!

[Christy Zhao 1H]

Keep in mind that the formal charge of the model should add up to the overall charge of the atom.

[Evelyn L 1H]

Also, if there must be a formal charge, elements like Oxygen which have a higher ionization energy are more likely than elements that have lower ionization energies (left, down) to have a charge.

[James Nguyen 3G]

When the formal charges are zero and the more electronegative / higher Ionization energy atoms are charged if the whole molecule has a charge.

[Madeline Musselman 3H]

When comparing the formal charges of structures of a compound, it is clear that the structure with a formal charge closest to zero is the most stable. To calculate the formal charge it is easiest by taking the elements number of valence electrons subtracted by number of bonds and additionally subtract lone pairs (by each electron)

[Ozhen Atoyan 1F]

To add on to the previous posts, the formal charge should also be the most favorable when the central atom has a formal charge of zero. This is due to the least electronegative atom being in the center. Thus, the central atom shouldn't have charges. It is better for the atoms around the central atom to have charges. The most electronegative atoms, which should be around the central atom should have charges such as, -1 or -2.

[Justin Lai 1C]

It is also really rare to have a formal charge of -2 in a stable lewis structure, so if the formal charge ends up being -2, try reducing the formal charge by adding bonds or drawing them a different way.