Chemical Bonding and Molecular Structure - Result Question 14
####14. Which of the following structures is the most preferred and hence of lowest energy for $SO_3$ ? (a)
(b)
(c)
(d)
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Solution:
- (d) The lowest energy structure is the one with the smallest formal charges on the atoms.
Option (b) and (c) are not possible structures of $SO_3$.
Formal charge $=$ total no. of valence $e^{-}$in the free atom - total no. of non-bonding (lone pair) $e^{-}-\frac{1}{2}$ (total no. of bonding $e^{-}$).
Formal charge on $S$ stom $=6-0-\frac{1}{2}(8)=+2$
Similarly, formal charges on coordinated bonded oxygen atom and covalently bonded oxygen atom are -1 and 0 respectively.
Formal charge on $S$ atom
$ =6-0-\frac{1}{2}(12)=0 $
Formal charge on $O$ atom
$ =6-4-\frac{1}{2}(4)=0 $
