Sulfur formal charge

The formal charge at sulfur can be reduced to 0 by including one double bond contribution. This change gives rise to two expanded octet structures ... 

The Ag-S bond length is 2.44 A. This value is also found in pyrargyrite and pyrostilpnite, both of which have the formula Ag5SbS3 and contain bicovalent silver and tercovalent argononic sulfur. It leads to 1.45 A for R for bicovalent silver with formal charge —1, which may be compared with the values 1.396 A and 1.528 A for silver with metallic valence 3 and 1, respectively (Pauling, 1960, p. 420). 

Because sulfur is from row 3, we determine how to optimize the structure by evaluating formal charge. Sulfur has six valence electrons (Group 16) and four assigned electrons (2 bonds + 2 lone-pair electrons) ... 

In this case, even with there being one double bond, the formal charge on the sulfur atom is +2, so structures that show two double bonds are possible, which can reduce further the positive formal charge. In order for structures such as... 

This structure is isoelectronic with (Si03)36 and (P03)33-. Gaseous S03 has a trigonal planar structure that has several contributing resonance structures. When the structure is drawn with only one double bond, the sulfur atom has a +2 formal charge that is relieved by stmctures having two double bonds. Therefore, multiple bonding is extensive. 

Next, we half-fill the lone unhybridized 3p orbital on sulfur and the lone 2p orbital on the oxygen atom with a formal charge of zero (atom B). Following this, the 2p orbital of the other two oxygen atoms (atoms C and D), are filled and then lone pairs are placed in the sp2 hybrid orbitals that are still empty. At this stage, then, all 24 valence electrons have been put into atomic and hybrid orbitals on the four atoms. Now we overlap the six half-filled sp2 hybrid orbitals to generate the cr-bond framework and combine the three 2p orbitals (2 filled, one half-filled) and the 3p orbital (half-filled) to form the four 7t-molecular orbitals, as shown below ... 

Write the Lewis structure of S03 in which the formal charge on each atom is 0. What is the shape of the molecule and what is the hybridization of the sulfur atom ... 

The sulfur atom of S02 has a formal charge of +1 and the singly bonded oxygen atom has a formal charge of — 1. We might therefore write the structure for S02 as... 

Draw three resonance structures for sulfur tetroxide, S04, whose connections are shown below. (This is a neutral molecule it is not sulfate ion.) Assign formal charges to the atoms in each structure. 

The formal charge on each oxygen in both ions is -1. The formal charge on sulfur in sulfate is +2 the charge on phosphorus is +1. The net charge of sulfate ion is -2 the net charge of phosphate ion is -3. 

Just as mild oxidation converts thiols to disulfides, vigorous oxidation converts them to sulfonic acids. KMn04 or nitric acid (HN03), or even bleach (NaOCl), can be used as the oxidant for this reaction. Any Lewis structure of a sulfonic acid requires either separation of formal charges or more than 8 electrons around sulfur. Sulfur can have an expanded octet, as it does in SF4 (10 electrons) and SF6 (12 electrons). The three resonance forms shown here are most commonly used. Organic chemists tend to use the form with an expanded octet, and inorganic chemists tend to use the forms with charge separation. 

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