Let us start this problem by drawing the Lewis structure of F3-.
Step 1: The steps that are required to be taken:
- Firstly, we need to calculate the total number of valence electrons that would be present in the structure. The number of valence electrons per atom of each element will be based on its group number. F is in group 7A so it has 7 valence electrons.
- One extra electron should be added for the negative charge present.
Atom Valence Electrons
Fluorine 7 e- x 3 = (21 e- ) + 1
= 22 valence e-
A total of 22 valence electrons are present.
Step 2 : The Lewis structures have to be drawn.
- All the atoms in F3- are equivalent; therefore, they can be drawn next to each other.
- You will then need to subtract two electrons for each bond.
- Then place the rest of the electrons in each fluorine atom to make sure the atom fulfills the octet.
- Finally, the two remaining electrons are placed in the central atom.
- The formal charge for each atom is then calculated using the equation
Formal Charge = group number – (bonds the element is making + non-bonding electrons)