# Lewis Dot Structure of the sulfite ion SO_{3}^{-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** SO _{3}^{-2}** .

What is the **SO _{3}^{-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 **SO _{3}^{-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** **SO _{3}^{-2}**

**Therefore, the structure in Step 1 is a plausible Lewis structure of SO _{3}^{-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 SO_{3}^{-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.

__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

__References__

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

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