Lewis Dot Structure of the sulfite ion SO3-2 - Electron Dot Structure

Lewis Dot Structure of the sulfite ion SO₃^-2

A simple method for writing Lewis Structures is given in a previous article entitled “Lewis Structures and the Octet Rule”.  

Several worked examples relevant to this procedure were given in previous posts please see the Sitemap - Table of Contents (Lewis Electron Dot Structures).

Let us consider the case of the sulfite ion. The chemical formula is SO₃^-2 . 

What is the SO₃^-2 Lewis structure?

 

Step 1: Connect the atoms with single bonds. The central atom is the sulfur atom.

 

Step 2: Calculate the # of electrons in π bonds (pi bonds, multiple bonds) using  formula (1): 

Where n in this case is 4 since SO₃^-2 consists of four atoms.

Where V = (6 + 6 + 6 + 6 ) – (-2) = 26 , V is the number of valence electrons of the ion.

Therefore, P = 6n + 2 – V = 6 * 4 + 2 – 26  = 0   There are no  π electrons in SO₃^-2

Therefore, the structure in Step 1 is a plausible Lewis structure of SO₃^-2.

Electrons are placed around each atom so that the octet rule is obeyed. Since S is a third row element can accommodate more than 8 valence electrons.

 

Step 3 & 4: The Lewis, resonance structures of SO₃^-2  are as follows:

 

 

Resonance Structures #1-#3 are more stable due to less charge separation - even though the S atom has more than 8 electrons (expanded octet) - comparing to Structure #4. Structure #4 is less stable because of larger charge separation.

 

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Relevant Posts - Relevant Videos

Lewis Structures|Octet Rule: A Simple Method to write Lewis Structures

Simple Procedure for writing Lewis Structures – Lewis Structures for sulfur trioxide (SO3)

Dot Structure |How do I draw a Lewis Structure for a molecule - Lewis Structure of Cyanamide

 

 

 

 

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References

1. G.N. Lewis, J.A.C.S, 38, 762-785, (1916)
2.  E. C. McGoran, J. Chem. Educ., 68, 19-23 (1991)
3. A.B.P. Lever, J. Chem. Educ., 49, 819-821, (1972)

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Key Terms

Lewis structures, electron dot structures, Lewis structures of the sulfite ion SO₃^-2, electron dot structures of the sulfite ion SO3-2, method for drawing Lewis structures,, chemistry, Chemistry Net

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