The Oxygen Group
The Oxygen Group
The Oxygen Group of the Periodic Table consists of the elements oxygen O, sulfur S, selenium Se, tellurium Te, and polonium Po. The outer electron structure ns2np4 characterizes all five of the elements, with n representing principal quantum numbers 2, 3, 4, 5, and 6, respectively. The ns2np4 indicates the possibility of oxidation states of −II, II, IV, and VI in all of the elements, with O almost always showing a value of −II. As one descends the group, non-metallic character gradually diminishes with only Po being distinctly metallic, and the crossover occurring with the metalloid or semi-metal Te. The II and the VI oxidation states decrease in stability down the group, and the IV oxidation state increases. Oxygen stands out as considerably different from the other elements, there being numerous discontinuities in properties between it and S. Covalent radii in pm are as follows: O(73), S(102), Se(117), Te(135), and Po (149). Ionic radii in pm are as: O−2(126), S−2(170), Se−2(184), and Te−2(207). a. E–pH diagrams. Figure 10.1 depicts the E–pH diagram for O with the soluble species (except H+) at 10−1.0 M. The upper region is occupied by O2, the lower region by H2, and the intermediate area by HOH and its equilibrium species H+ and OH−. This diagram functions as the background for all chemical reactions in HOH solution and in an air or O2 atmosphere. The compound hydrogen peroxide H2O2 is another compound of O and H which is of importance. Because of complicated kinetic behavior, H2O2 can act as either an oxidant or a reductant. Figure 10.2 displays the E–pH diagram for H2O2 at 10−1.0 M when it is functioning as an oxidizing agent. Figure 10.3 is the E–pH diagram for H2O2 at 10−1.0 M when it is acting as a reducing agent. Equations for the lines that separate the species are displayed in the legends of the diagrams.
Oxford Scholarship Online requires a subscription or purchase to access the full text of books within the service. Public users can however freely search the site and view the abstracts and keywords for each book and chapter.
If you think you should have access to this title, please contact your librarian.