Atomic covalent

Network covalent Atoms — Covalent bond Hard solids with very high melting points noncon- C... 

Using the carbon atom covalent radius 0.77 A and the covalent radii given in Figure 19-3, predict the C—X bond length in each of the following molecules CF<, CBr4, CI4. Compare your calculated bond lengths with the experimental values C—F in CF4 = 1.32 A, C—Br in CBr = 1.94 A, C—I in CI4 = 2.15 A. 

Network solids consist of atoms covalently bonded to their neighbors throughout the extent of the solid. 

Mercuryd) compounds containing a covalent Hg—Hg bond are well known, but those containing more than two Hg atoms covalently bonded are rare. 

Schematic diagrams for adsorption geometries of (c) and (e) are shown in (d) and (f), respectively a linear atop and a tilted off-site CO are implicated. The black (red) circles represent carbon (oxygen) atoms and the large gray circles are silver atoms. The sizes of the circles are scaled to the atomic covalent radii. (Reprinted with permission from Ref. [25]. Copyright 2001, The American Physical Society.)...

The familiar diamond structure, with each atom covalently bonded in a perfect tetrahedral fashion to its four neighbors, is adopted not only by C but also by Si and Ge. Silicon can also adopt a wurtzite structure (see below), an example of a polytype (one of several crystal structures possible for a substance having an identical chemical composition but differing in the stacking of layers, and which may exist in a metastable state after its formation at some different temperature or pressure). 

Simple molecules are made up of small groups of atoms, covalently bonded together in a molecule. Although the covalent bonds between the atoms are very strong, there are only weak forces between the molecules. 

The half of intemuclear distance (for binary bond) of similar atoms or atomic, covalence or ionic radii (depending upon bond type) can be used as a dimensional characteristic of atoms. 

Covalent Network atoms covalent bonds very high low hard crystals that are insoluble in most liquids formed usually from elements belonging to Group 14 (IV A) graphite, diamond, Si02... 

Because surfaces of ribosomal particles have a variety of potential binding sites for such clusters, attempts are in progress to bind heavy-atoms covalently to a few specific sites on the ribosomal particles prior to crystallization. This may be achieved either by direct interaction of a heavy-atom cluster with chemically active groups such as -SH or the ends of rRNA on the intact particles or by covalent attachment of a cluster to natural or tailor-made carriers that bind specifically to ribosomes. 

Covalent Atoms Covalent bonds Diamond (carbon) Paper 0.3... 

Cosmic Radiation charged atomic particles originating from space Covalent Bond chemical bond in which electrons are shared between atoms Covalent Crystal crystal in which atoms are held together by covalent bonds in a rigid three-dimensional network, for example, diamond... 

In covalent bonds, the electrons are shared between two atoms resulting in a buildup of electron density between the atoms. Covalent bonds are strong and directional. 

Electrons occupy distinct orbitals within atoms (see Chapter 4 for details). When atoms covalently bond to form molecules, the shcired electrons cire no longer constrained to those atomic orbitals instead, they occupy molecular orbitals, larger regions that form from the overlap of atomic orbitals. Just as different atomic orbitals are associated with different levels of energy, so cire molecular orbitals. A stable covalent bond forms between two atoms because the energy of the moleculcir orbital associated with the bond is lower than the combined energies associated with the atomic orbitals of the sepcirated atoms. 

In this case the electropositive sodium atom loses its 3s electron, which is then transferred to the 2p orbital of the electronegative fluorine atom to produce the Na+F ion-pair. Ionic bonding is the subject of Chapter 7. When there is little or no difference in the electronegativity coefficients of the combining atoms, covalent bonds are possible in which two or more electrons are shared between the two atoms. Covalency is the main subject of this chapter. 

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