Question 7.10: Calculate the formal charge on each atom in the following el......

STRATEGY

Considering each atom separately, find the number of valence electrons on the atom (the periodic group number). Then subtract half the number of bonding electrons and all the nonbonding electrons.

For sulfur:\quad\quad\quad \text{Isolated sulfur valence electrons} \quad\quad 6\\ \quad\quad\quad\quad\quad\quad\quad \text{Bound sulfur bonding electrons}\quad\quad 6 \\ \quad\quad\quad\quad\quad\quad\quad\text{Bound sulfur nonbonding electrons}\quad\quad 2\\ \quad\quad\quad\quad\quad\quad\quad \text{Formal charge }  = 6  –  \frac{1}{2} (6)  –  2  =  +1

For singly bonded oxygen: \quad\quad\quad\text{Isolated oxygen valence electrons}\quad\quad 6 \\ \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad \text{Bound oxygen bonding electrons}\quad\quad 2\\ \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\text{Bound oxygen nonbonding electrons}\quad\quad 6 \\ \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad \text{Formal charge }  = 6  –  \frac{1}{2} (2)  –  6  =  -1

For doubly bonded oxygen:\quad\quad\quad\text{Isolated oxygen valence electrons}\quad\quad 6\\ \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad \text{Bound oxygen bonding electrons}\quad\quad 4\\ \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\text{Bound oxygen nonbonding electrons}\quad\quad 4 \\ \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad \text{Formal charge }  = 6  –  \frac{1}{2} (4)  –  4  =  0

The sulfur atom of  SO_{2}  has a formal charge of +1 and the singly bonded oxygen atom has a formal charge of -1 We might therefore write the structure for  SO_{2}  as