Covalent bonds carbon

Strategy We know that hydrogen forms one covalent bond, carbon forms four, and oxygen forms two. Trial and error, combined with intuition., is needed to fit the atoms together. 

Replacement of each water molecule by an MnAli2 icosahedron with shared faces leads to an infinite framework with 136 Mn and 816 Al atoms in the unit cube. This framework is similar to the framework of covalently bonded carbon atoms in a diamond crystal, with one body diagonal of each pentagonal dodecahedron in place of each C—C covalent bond. 

This determination of the molecular geometry of carbon dioxide and water also accounts for the fact that carbon dioxide does not possess a dipole and water has one, even though both are composed of polar covalent bonds. Carbon dioxide, because of its linear shape, has partial negative charges at both ends and a partial charge in the middle. To possess a dipole, one end of the molecule must have a positive charge and the other a negative end. Water, because of its bent shape, satisfies this requirement. Carbon dioxide does not. 

Many hydrate cavities have analogs (1) in the clathrasils in which SiC>2 replaces water as a host molecule (Gerke and Gies, 1984) and (2) in the Buckminsterfullerene (covalently bonded carbon cavities) family (Curl and Smalley, 1991). Even with these analogous structures providing estimates of other cavities, for hydrate unit crystals there is the additional restriction that the cavities must be packed to fill space. 

Carbon is the most versatile element in forming allotropes. Organized or unorganized, atoms of carbon can take on an incredible number of arrangements, each different from the other and each forming a different allotrope. With all their diversity, these substances have one thing in common they are made up solely of covalently bonded carbon atoms. 

Another allotrope of elemental carbon is diamond. Besides being blinded by the brilliance of a cut diamond, you should know that diamond is the hardest natural substance. It s often used on the tips of cutting tools and drills. Can the structure of diamond explain its hardness Look at the model of diamond. Every carbon atom is attached to four other carbon atoms which, in turn, are each attached to four more carbon atoms. Diamond is one of the most organized of all substances. In fact, every diamond is one huge molecule of carbon atoms. This organization of covalently bonded carbons throughout diamond accounts for its hardness. If you tried to write... 

Organic chemistry is the study of carbon (C) compounds, all of which have covalent bonds. Carbon atoms can bond to each other to form open-chain compounds, Fig. 1.1(a), or cyclic (ring) compounds, Fig. 1.1(c). Both types can also have branches of C atoms, Fig. 1.1(b) and (d). Saturated compounds have C atoms bonded to each other by single bonds, C—C unsaturated compounds have C s joined by multiple bonds. Examples with double bonds and triple bonds are shown in Fig. 1.1(c). Cyclic compounds having at least one atom in the ring other than C (a heteroatom) are called heterocyclics, Fig. 1.1 (/). The heteroatoms are usually oxygen (O), nitrogen (N), or sulfur (S). 

Covalent solids. The units that comprise a covalent solid are atoms held together by covalent bonds. They have very high melting points (1200°C to 2000°C or more is not unusual) and are extremely hard. They are insoluble in most solvents. Diamond is a covalent solid composed of covalently bonded carbon atoms. Diamonds are used for industrial cutting because they are so hard and as gemstones because of their crystalline beauty. 

Of the solids given, ionically bonded sodium chloride is expected to be crystalline, a poor electrical conductor in the solid form, and a good conductor when fused. Diamond, formed of covalently bonded carbon atoms, is a network substance that does not form cubic crystalline patterns, and does not conduct electricity either when solid or fused. None of the allotropic forms of sulfur is expected to conduct electricity. Choice (D), the metal chromium, could possibly form a cubic solid crystalline form, but can be eliminated because it is expected to conduct electricity both when a solid and when fused. The correct choice is (A), because sodium chloride is a crystalline solid that is a poor conductor in the solid state and a good conductor when fused. ... 

The hundreds of thousands of organic molecules have various chemical and physical properties and three-dimensional structures. However, certain similarities exist. Organic compounds, of course, are covalently bonded, carbon based molecules. The ability of carbon atoms to bond with one another allows the formation of long chains, double and triple bonds, and even rings. 

Brill, R. (1950) The covalent bond in diamond and the X-ray scattering factor of covalent,-bonded carbon. Acta Cryst., 3, 333-337. 

CNTs are considered to be ideal candidates for a wide range of apvplications in materials science because of their exceptional mechanical, thermal, and electronic properties (Baughman Zakhidov, 2002). Carbon nanotubes exist as two types of structures singlewall carbon nanotubes (SWNTs) and multiwall carbon nanotubes (MWNTs). Fig. 1 shows the schematic pictures of different types of carbon nanotubes. SWNT can be considered as graphene sheet rolled cylinders of covalently bonded carbon atoms with very high aspect ratios of 1000 or more. MWNTs consist of a number of graphene cylinders concentrically nested like rings in a tree trunk with an interlayer distance of -0.34 nm. 

---