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What are the formal charges on each atom in sulphite, SO32 and chlorite, ClO2 ions?

Answer
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Hint: Formal charge is a theoretical value assigned to an atom in a molecule which reflects the equal sharing of electrons in a chemical bond, neglecting the electronegativity difference between the atoms. Sketch the Lewis diagram for the given ions to find the value of formal charge of each atom.

Complete answer:
The formal charge can be assigned to an atom with the help of following formula:
 F=VNB2(i)
Where, F is the formal charge on the atom, V is the number of electrons of atom in its ground state, N is the number of lone pair of electrons present on the atom and B is the number of bonding electrons in that atom.
The Lewis structure for sulphite ions is as follows:
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Formal charge for sulphur atom:
Number of electrons of sulphur in its ground state =6
Count of nonbonded electrons present on sulphur atom =2
Number of bonding electrons =8
Substituting values in equation (i) , formal charge of sulphur atom will be as follows:
  F=6282
 F=0
Formal charge for doubly bonded oxygen atom:
Number of electrons of oxygen in its ground state =6
Count of nonbonded electrons or number of lone pair of electrons present on oxygen atom =4
Number of bonding electrons =4
Substituting values in equation (i) , formal charge of sulphur atom will be as follows:
  F=6442
 F=0
Formal charge for single bonded oxygen atoms:
Number of electrons of oxygen in its ground state =6
Count of nonbonded electrons or number of lone pair of electrons present on oxygen atom =6
Number of bonding electrons =2
Substituting values in equation (i) , formal charge of sulphur atom will be as follows:
  F=6622
 F=1
Hence, in sulphite ions, the formal charge of sulphur atom, doubly bonded oxygen atom and singly bonded oxygen atoms is 0,0 and 1 respectively.
The Lewis structure for chlorite ions is as follows:
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Formal charge for chlorine atom:
Number of electrons of chlorine in its ground state =7
Count of nonbonded electrons present on chlorine atom =4
Number of bonding electrons =6
Substituting values in equation (i) , formal charge of sulphur atom will be as follows:
  F=7462
 F=0
Formal charge for doubly bonded oxygen atom:
Number of electrons of oxygen in its ground state =6
Count of nonbonded electrons or number of lone pair of electrons present on oxygen atom =4
Number of bonding electrons =4
Substituting values in equation (i) , formal charge of sulphur atom will be as follows:
  F=6442
 F=0
Formal charge for single bonded oxygen atom:
Number of electrons of oxygen in its ground state =6
Count of nonbonded electrons or number of lone pair of electrons present on oxygen atom =6
Number of bonding electrons =2
Substituting values in equation (i) , formal charge of sulphur atom will be as follows:
  F=6622
 F=1
Hence, in chlorite ions, the formal charge of chlorine atom, doubly bonded oxygen atom and singly bonded oxygen atom is 0,0 and 1 respectively.

Note:
Lewis structures in which the formal charges are zero for most atoms in the compound, are more preferably considered than the one with non-zero formal charges. Moreover, the negative formal charge should be present on the most electronegative element in the compound.