Question

In the given, Lewis structure of ${S_2}O_3^{ - 2}$ formal charge present on the sulphur atoms 1 and 2 respectively,

(A) Zero, +1
(B) +1, +1
(C) +2, +2
(D) Zero, Zero

Answer 1

Hint: The formal charge on a particular atom is the quantity of valence electrons around that atom and number atom bonded to it. To solve this question we should know the formula to calculate the formal charge.

Complete step by step answer:
The formal charge is the number of charges on an atom in a molecule, under the assumption that electrons in all bonds are equally shared irrespective of the relative electronegativity.
Formula of formal charges:
Formal charge = (number of valence electron in free atom) - (number of lone pair electrons) - ($\dfrac{1}{2}$number of bond pair electrons)
-Formal charge present on sulphur atom 1:
Number of valence electrons in sulphur 1 = 6
Number of lone pair electrons in sulphur 1= 4
Number of bond pair electrons in sulphur 1 = 4
Substituting the values in the formula,
 Formal charge on sulphur 1 = 6 - 4 - 2
 = 0
Therefore, the formal charge on sulphur 1 is 0.

- Formal charge on sulphur 2:
Number of valence electrons in sulphur 2 = 6
Number of lone pair electrons on sulphur 2 = 0
Number of bond pair electrons on sulphur 2 = 12
Formal charge = (number of valence electron in free atom) - (number of lone pair electrons) - ($\dfrac{1}{2}$ number of bond pair electrons)
Substituting in the value in the formula,
Formal charges on sulphur 2 = 6 - 0 - 6
= 0
Therefore, the formal charge on sulphur 2 is 0.
The option D is 0,0.

Thus, option D is the correct answer.

Note: The calculation of formal charge will be correct when the molecule is represented in Lewis dot structure. Sometimes the calculation may go wrong because of counting the number of bonding pair electrons or number of lone pair electrons of the atom.