Among the fullerenes, one of the most common "molecule" has 60 C atoms, and is represented by C60, a diagram is shown here. If you connect the 60 carbon atoms with bonds, the structure looks like a cage with 5- and 6- member rings. Synthesis, bonding, symmetry and stability of the cagelike fullerenes have already attracted a lot of attention, and their properties are even more fascinating.
Regarding carbon compounds, you already know something about CO2 and CO including their roles in the environment. The hard carbides such as Fe3C, WC, and TiC are more interesting to material scientists and engineers for their application in cutting tools. The calcium carbide CaC2 produced by reducing CaO by carbon was a valuable commodity at one time due to its reaction with water to give acetylene gas:
By weight, silicon is the most abundant element in the Earth's crust. It usually exists in the form of oxide, SiO2. This formula does not do justice to represent so many different materials we call silicates, but these substances are indeed SiO2. Some of the minerals contain impurities.
In pure form, SiO2 is quartz. Small particles of quartz are sand. They are hard. In the structure at the atomic level, every silicon atom is bonded to 4 oxygen atoms, and every oxygen is bonded to two Si atoms. The four Si-O bonds point towards the corner of a tetrahedron, as do the C-C bonds in the diamond structure. When impurity is present, the quartz may be colored. Due to various arrangement of the Si-O-Si bonds, the same substance appear in many forms.
A basic unit of silicate structures is SiO44-. The gemstone zircon has a formula ZrSiO4, and olivine has a chemical formula of (MgFe)2SiO4. Two SiO44- units combine to give the pyrosilicate unit Si2O76-, and it appears in akermanite, Ca2MgSi2O7. When the number of units increase, the tetrahedral units combine to form rings, chains, layers and 3-dimensional networks. Thus, the structure and classification of silicate is a major part of minerals. This site has some interesting pictures.
Elemental silicon can be obtained from reduction of silicates. The reduction of sand, SiO2 by carbon at 3300 K in the reaction,
If a more reactive element, Mg, is used in the reduction, Mg2Si is formed,
Silane, SiH4, can be produced by reacting Mg2Si with acids
When chlorine pass through hot sand (SiO2) and carbon, SiCl4 is produced,
CH3 CH3 CH3 -O-Si--O--Si--O--Si--O-- CH3 CH3 CH3Of course, the 4 bonds around the Si atoms points to the corners of a tetrahedron. These siloxane polymers are widely used as sealants, adhesives, additives, flame retardants, and lubricants. They have a wide application in industries. Depending on the organic group attached to silicon, the inorganic polymer Silicones has been an important class of materials.
Polymers are really interesting, but there are so many kinds of them that make you wonder if you ever become an expert on it.
a B Al Ga In Tl b C Si Ge Sn Pb c N P As Sb Bi d O S Se Te Po e F Cl Br I AtAnswer b
Diamond is the hardest thing in the world. Fullerenes are large molecules consisting of 40 to hundreds of carbon atoms, with C60 being the most common.
Answer . . . CaC2
The reaction to produce acetylene gas is
Answer ... C
Carbon or coke is used for silicon metal, because Mg2Si is formed if Mg is used.
Answer ... methane is stable
Methane is the major component of natural gas, and it will not react with air until ignited, whereas silane ignites explosively as soon as it contacts air.
Silicon polymers are a important class of materials invented not too long ago.
Answer ... 4
Silicon and diamond have the same crystal structure. The edge of unit cells of Si is larger than that of diamond.