Fluorine, elemental oxyacids

Carbon is the basis of organic chemistry there are more compounds of carbon than of any other element except hydrogen and possibly fluorine. However, most of the chemistry of carbon is the province of organic chemistry and thus not covered in this encyclopedia. The inorganic chemistry of carbon discussed in this article, which is an update of an excellent article written previously by professor R. Bruce King (University of Georgia, Athens), includes the allotropic forms of elemental carbon, simple molecular carbon halides and oxides, carbon oxyacids and oxyanions, carbon snlfur derivatives, simple cyano derivatives, and carbon-based molecnlar ladders. 

An acid is a distinct type of molecular compound. Most acids used in the laboratory can be classified as either binary acids or oxyacids. Binary acids are acids that consist of two elements, usually hydrogen and one of the halogens— fluorine, chlorine, bromine, iodine. Oxyacids are acids that contain hydrogen, oxygen, and a third element (usually a nonmetal). 

There has been general agreement that bonds to fluorine, chlorine, methyl, or phenyl groups in hypervalent compounds should be described as single polar covalent bonds and that the central atoms therefore must acconunodate more than four electron pairs in its valence shell. But there has been a curious reluctance to accept that bonds from the central atom to terminal oxygen atoms in the oxides or oxyacids of the Group 15, 16, or 17 elements, such as SO2 SO3, or H2SO4, are best described as double (two electron pair) bonds and that the central atoms in these compounds also must accommodate more than four electron pairs in their valence shells. 

---