Group 4A elements Carbon

Organic chemistry, then, is the study of carbon compounds. But why is carbon special Why, of the more than 30 million presently known chemical compounds, do more than 99% of them contain carbon The answers to these questions come from carbon s electronic structure and its consequent position in the periodic table (Figure 1.1). As a group 4A element, carbon can share four valence electrons and form four strong covalent bonds. Furthermore, carbon atoms can bond to one another, forming long chains and rings. Carbon, alone of all elements, is able to form an immense diversity of compounds, from the... 

The group 4A elements—carbon, silicon, germanium, tin, and lead—are especially important, both in industry and in living organisms. Carbon is present in all plants and animals, accounts for 23% of the mass of the human body, and is an essential constituent of the molecules on which life is based. Silicon is equally important in the mineral world It is present in numerous silicate minerals and is the second most abundant element in the earth s crust. Both silicon and germanium are used in making modern solid-state electronic devices. Tin and lead have been known and used since ancient times. 

Figure 7.17 shows samples of the Group 4A elements. Carbon, the first member of the group, is a nonmetal, whereas silicon and germanium, the next two members, are metalloids. Tin and lead, the last two members of the group, are metals. They do not react with water, but they do react with aqueous acid to produce hydrogen gas ... 

Group 4A elements, such as carbon, have four valence electrons and form four bonds, as in methane, CH4. The carbon atom in the resultant molecule has four bonding pairs of electrons. 

The group 4A elements exemplify the increase in metallic character down a group in the periodic table Carbon is a nonmetal silicon and germanium are semimetals and tin and lead are metals. The usual periodic trends in atomic size, ionization energy, and electronegativity are evident in the data of Table 19.4. 

The group 4A elements—C, Si, Ge, Sn, and Pb—exhibit the usual increase in metallic character down the group. Their most common oxidation state is +4, but the +2 state becomes increasingly more stable from Ge to Sn to Pb. In elemental form, carbon exists as diamond, graphite, fullerene, coke, charcoal, and carbon black. 

Sketch the electron populations of the bands of MO energy levels for elemental carbon (diamond), silicon, germanium, gray tin, and white tin. (Band gap data are given in Table 21.3.) Your sketches should show how the populations of the different bands vary with a change in the group 4A element. 

Find a flowering plant that interests you. Look at the root formation, leaf shapes and how they are attached to the stem, and the shape of the flower. Draw these different shapes. Find molecules that resemble these different shapes. Remember that group 3A elements form trigonal planar shaped molecules, group 4A elements form tetrahedral shaped molecules, group 5A elements form pyramid shaped molecules and group 6A elements form bent shaped molecules. Carbon chains have a zigzag shape and the DNA molecule is a double helix. You will see that these molecular shapes are duplicated in natural objects. See how many molecular shapes you can find in an ordinary flower. 

The Group 4A elements form compounds in both the +2 and +4 oxidation states. For carbon and silicon, the +4 oxidation state is the more stable one. For example, CO2 is more stable than CO, and Si02 is a stable compound, but SiO does not exist under normal conditions. As we move down the group, however, the trend in stability is reversed. In tin compounds the -1-4 oxidation state is only slightly more stable than the + 2 oxidation state. In lead compounds the -1-2 oxidation state is unquestionably the more stable one. The outer electron configuration of lead is 6s 6p, and lead tends to... 

Consider the elements of Group 4A (the "carbon family") C, Si, Ge, Sn, and Pb. What is the trend in metallic character as one goes down this group What is the trend in metallic character going from left to right across a period in the periodic table ... 

The group 4A elements possess the outer-shell electron configuration ns np. The electronegativities of the elements are generally low (V TABLE 22.8) carbides that formally contain C ions are observed only in the case of a few compounds of carbon with ver)y active metals. Formation of 4-1- ions by electron loss is not observed for any of these elements the ionization energies are too high. The +2 oxidation state is found in the... 

CARBON, THE OTHER GROUP 4A ELEMENTS, AND BORON (sections 22.9, 22.10, 22.11)... 

The group 4A elements exhibit the most versatile bonding of all elements. As we saw in Chapter 20, carbon has the ability to bond with other carbon atoms and with a few other elements to form a great variety of organic compounds. These compounds are the molecules of life, which we examined in Chapter 21. Here we focus on elemental carbon and those compounds of carbon that are known as inorganic (rather than organic). 

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