Carbon, Nitrogen, Oxygen, Phosphorus, and Sulfur

Sulfur is a yellow solid that exists as several allotropes that form when sulfur is heated to different temperatures. Elemental sulfur is found in nature in underground deposits and is mined by the Erasch Process, which uses hot water to melt the sulfur so that is can be forced to the surface with compressed air. Most of the mined sulfur is used to make sulfur dioxide (SOj). The most important compound of sulfur is sulfuric acid (H2SO4). This compound is made by converting SO2 to SO3 and then reacting the SO3 with water. Sulfuric acid is the largest volume chemical produced in this United States. 

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T Figure 2.24 The elements that are essential for life are indicated by colors. Red denotes the six most abundant elements in living systems (hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulfur). Blue indicates the five next most abundant elements. Green indicates the elements needed in only trace amounts. 

Carbon, nitrogen, oxygen, phosphorus, and sulfur—a cluster of nonmetals in the periodic table (Figure 5.5)—are extremely important elements. Carbon is important because it is the element upon which all life is based. All organic compounds, which encompasses nearly all 13 million compounds that exist (see Chapter 14), contain carbon. Elemental carbon exists as several different allotropes, or different forms of the same element. These include diamond, graphite, and buckminsterfullerene, which is a form more recently synthesized. Inorganic compounds of carbon are also important. These include... 

Although benzenes substituted by six carbon, nitrogen, oxygen, silicon, and sulfur are well known [23-29], such compounds are exceptionally limited in the field of phosphorus chemistry. Benzenes carrying six phosphorus substituents have not been synthesized and only limited compounds such as tetraphosphoryl- [30, 31] or tetraphosphinobenzenes [32], tetraphosphorylquinone [33, 34], tetraphosphoryl-cyclobutadiene complexes [35, 36], and pentaphosphinocyclopentadienyl complexes [37] have been reported (Scheme 20). 

In this chapter, the biogeochemical cycling of organic matter is discussed from the perspective of its carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur content. 

In addition to carbon and hydrogen, the key elements in the molecules of life include nitrogen, oxygen, phosphorus, and sulfur. Also, a family of trace elements is required sodium, potassium, magnesium, manganese, calcium, chlorine, fluorine, iodine, iron, copper, nickel, cobalt, zinc, molybdenum, silicon and vanadium. 

Carbohydrates, proteins, fats, and nucleic acids are composed of six elements carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. In addition to these, many other minerals are required for experimental mammals, and presumed to be required for humans. These are divided into two groups, bulk and trace elements, and are found in Table 23-7. Table 23-8 lists some elements whose functions are known, or whose deficiencies result in well-recognized symptoms. 

Many of the non metals such as hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, chlorine, and iodine are essential elements, and most are used in quantities for beyond the trace levels. Nevertheless, most of the chemistry of these elements in biological systems is more closely associated with organic chemistry than with inorganic chemistry. 

The poor metals among the BCNOs usually include aluminum, gallium, indium, thallium, tin, lead, and bismuth. The metalloids are boron, silicon, germanium, arsenic, antimony, tellurium, and polonium. The nonmetals are carbon, nitrogen, oxygen, phosphorus, sulfur and selenium. These groups are not official, and chemists sometimes disagree on whether a particular element like boron should be called a metal or a metalloid. 

Living cells depend principally on a supply of carbon, oxygen, nitrogen, hydrogen, phosphorus, and sulfur. In addition their biochemistry... 

Formulas that show the connections in this way are known as structural formulas, whereas formulas that give just one symbol for each element present are called molecular formulas. The molecular formula for methane is GH, for example. Methane and the many millions of compounds that contain carbon combined with hydrogen— and often also with nitrogen, oxygen, phosphorus, or sulfur—are known as organic compounds. 

The octet rule accounts for the valences of many of the elements and the structures of many compounds. Carbon, nitrogen, oxygen, and fluorine obey the octet rule rigorously, provided there are enough electrons to go around. However, some compounds have an odd number of electrons. In addition, an atom of phosphorus, sulfur, chlorine, or another nonmetal in Period 3 and subsequent periods can accommodate more than eight electrons in its valence shell. The following two sections show how to recognize exceptions to the octet rule. 

Nonmetals carbon, nitrogen, oxygen, silicon, phosphorus, sulfur, chlorine, bromine, and iodine... 

Figure 4.19 Molecules of phosphorus and sulfur with multiple bonds to carbon, nitrogen, and oxygen.

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