Lewis Electron Dot Structure of sulfur trioxide SO3
A simple procedure for writing Lewis Structures was 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).
Consider the case of sulfur trioxide, SO3. SO3 is used for the industrial production of sulfonates - organic compounds with a sulfur carbon bonds - when it reacts with organic compounds. A well known and mass produced sulfonate is sodium dodecylbenzenesulfonate (also commonly referred to as linear alkylbenzene sulfonate or LAS) which is a series of organic compounds with the formula C12H25C6H4SO3Na. It is a colourless salt with useful properties as a surfactant. It is usually produced as a mixture of related sulfonates. LAS is a major component of laundry detergent.
Step 1: The central atom will be the S atom since it is the less electronegative. Connect the atoms with single bonds:
Step 2: Calculate the # of electrons in π bonds (multiple bonds) using formula (1) :
Where n in this case is 4 since SO3 consists of four atoms.
Where V = (6 + 6 + 6 + 6) = 24 Therefore, P = 6n + 2 – V = 6 * 4 + 2 – 24 = 2 So there are 2 π electrons in SO3 and therefore 1 double bond must be added to the structure of Step 1.
Step 3 & 4: One double bond must therefore be placed through the 3 S-O bonds. Therefore, the Lewis structures of SO3 are as follows:
The above simple procedure for drawing Lewis electron dot structures is also shown in the following video:
- 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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