Scientific Tutor

What is formal charge?

Formal charge is a technique to compare the original valence electrons of an atom to the number of valence electrons that remain close to each individual atom at the end of forming the electron dot structure (Lewis structure).

How do you determine the formal charge?

To determine the formal charge take the original number of valence electrons and subtract the number of electrons closest to the atom after the electron dot structure (Lewis structure) is complete. To achieve this draw a box around each atom and the electron lone pairs. This box should also cut the bonds to other atoms in half (essentially returning half the electrons in one bond to one atom and half to the other). Do this for each atom in the electron dot structure (Lewis structure).

For each atom on the Lewis Structure:

Original valence electrons – Remaining electrons = Formal Charge

Examples: Give the formal charge of each atom in the Lewis Structure. VIDEO Formal Charge Examples 1.

PRACTICE PROBLEMS: Give the formal charge of each atom in the electron dot structure (Lewis structure).