Question

Question #c2852

Answer 1

Valence of Sulfur in `SO_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"Charges" = 0` => `S + 2"Oxy"` = `S + 2(-2)` = `0` => `S = +4`

Formal Charge of S in `SO_2`:
Contributing resonance structures for `SO_2` include ...

`:ddotO=ddotS-ddotO:: <=> ::ddotO-ddotS=ddotO:`

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

`FC = "Valence" - (("Bonded" "Electrons")/(2)) - "NonBonded""Electrons"`

`FC(-ddotS=) => 6 - (6)/2 - 2 = +1`

`FC(- ddotO:: ) => 6 - 2/2 - 6 = -1`

`FC(= ddotO: ) => 6 - 4/2 - 4 = 0`

Net Charge = `FC(-ddotS=) + FC(- ddotO:: ) + FC(= ddotO: )`#

`= (+1) + (-1) + (0) = 0`