Question c2852

Jul 5, 2017

Valence of Sulfur in $S {O}_{2}$ is 6 but the Formal Charge is +1 for the contributing resonance structures. However, calculating the charge associated with sulfur compound, then valency = +4.

Explanation:

Valence of Sulfur:
Valence of S = 6 as it is in Group VIA of the Main Group Elements of the Periodic Chart and specifies 6 valence electrons. It's electron configuration is ... S: [Ne]3s^2"3p^4 with 2 electrons in the s-orbital and 4 electrons in p-orbitals.

In terms of Valency,
Sulfur is carrying a +4 charge.

That is, $\Sigma \text{Charges} = 0$ => $S + 2 \text{Oxy}$ = $S + 2 \left(- 2\right)$ = $0$ => $S = + 4$

Formal Charge of S in $S {O}_{2}$:
Contributing resonance structures for $S {O}_{2}$ include ...

$: \ddot{O} = \ddot{S} - \ddot{O} : : \iff : : \ddot{O} - \ddot{S} = \ddot{O} :$

Formal Charge (FC) on Sulfur is calculated using the formula...

$F C = \text{Valence" - (("Bonded" "Electrons")/(2)) - "NonBonded""Electrons}$

$F C \left(- \ddot{S} =\right) \implies 6 - \frac{6}{2} - 2 = + 1$

$F C \left(- \ddot{O} : :\right) \implies 6 - \frac{2}{2} - 6 = - 1$

$F C \left(= \ddot{O} :\right) \implies 6 - \frac{4}{2} - 4 = 0$

Net Charge = $F C \left(- \ddot{S} =\right) + F C \left(- \ddot{O} : :\right) + F C \left(= \ddot{O} :\right)$

$= \left(+ 1\right) + \left(- 1\right) + \left(0\right) = 0$