Molecular Geometry of Sulfur Dioxide (SO2)
The molecular formula of sulfur dioxide (SO2) shows that it has one sulfur (S) atom and two oxygen (O) atoms. Sulfur and oxygen are located in Group 16 of the periodic table. Both have six valence electrons. Oxygen requires two electrons to complete its octet and acquire the electron configuration of its nearest inert gas neighbor, neon [1-4].
Sulfur is the least electronegative atom among the two and will occupy the central position. Each oxygen atom will form a double covalent bond with the sulfur atom. Therefore, the sulfur dioxide molecule consists of two S-O double bonds. Sulfur will use four of its six valence electrons to form the two double bonds, leaving one lone pair. In the Lewis structure, the dash represents chemical bonds, and the dots represent lone pairs.
VSEPR theory can predict the shape of the sulfur dioxide molecule. Three substituents (two oxygens and one lone pair) are attached to the central sulfur atom. Therefore, the steric number of sulfur is 3. These three groups are approximately 120° apart, corresponding to a trigonal planar geometry. Since one of these substituents is a lone pair, the shape will be distorted. The exact shape of SO2 is angular or bent with a bond angle of 119°. Both sulfur and oxygen are sp2 hybridized. The VSEPR notation of sulfur dioxide is AX2E1.