Question #c2852

1 Answer

Answer:

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#