Sharing of electrons

The second formula means merely that the HC1 molecule is a resonance hybrid between the ionic molecule H+Cl and the molecule with the purely covalent bond, the direction of the arrow giving the direction in which the electrons have, on the average, been displaced (66). As, however, such an arrow is used by others (57), for indicating a coordinate link (semipolar double bond) caused by a lone electron pair of the donor atom, which likewise produces a dipole with its positive end on the donor side and its negative one on the acceptor side, the author suggests that the symbol — be used for the normal covalent bond, which, by resonance with an ionic structure, possesses a dipole. The point of this half arrow also indicates the direction of the negative end of the dipole. The full arrow — will then be reserved for the coordinate link. Both links play their roles in chemisorption, and it may be useful for the purposes of this article to introduce relatively simple symbols. According to this principle HC1 should be formulated as H—1-Cl. 

In many cases of chemisorption normal covalent bonds are formed, where an electron of the adsorbed atom and one of the metal form a pair. The adsorbed atoms share their electrons either with the atoms of the metal on which they are adsorbed or with the metal as a whole. They form dipoles on the surface of the metal, and the direction of these dipoles are of great importance for chemisorption and catalysis. 

Just as a metal may play the role of a halogen atom in the adsorption of alkali ions discussed in the previous section, it may in other cases act similarly to the chlorine atom in HC1 and form a covalent bond. Hydrogen atoms adsorbed on the surface of platinum may serve as an example. The dipoles point with their positive ends away from the metal and may 

In other cases the adsorption of hydrogen atoms results in surface hydride dipoles pointing with their negative ends away from the metal, as is observed in the adsorption on nickel, 

The free molecules of metallic oxides can best be described as having covalent links, possessing dipoles (58). Similarly oxygen atoms adsorbed on metallic surfaces form covalent bonds, sharing two pairs of electrons with the metal (59) or with one specific atom or two atoms of the metal. Their dipoles point with the negative ends away from the metal. We may, to give an example, express the situation of the adsorption of oxygen on silver by 

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Covalent bonds are formed by the sharing of electrons. Thus the carbon atom, with four equivalent electrons shares with the electrons from four hydrogen atoms. 

Co-ordinate bonds are formed by the sharing of electrons, both electrons being donated by the same atom. Thus the hydrogen ion, has no outer electrons whilst ammonia has eight, six shared with hydrogen atoms and one lone-pair. This lone-pair is donated to the hydrogen ion and the ammonium ion is formed ... 

There are many compounds which do not conduct electricity when solid or fused indicating that the bonding is neither metallic nor ionic. Lewis, in 1916. suggested that in such cases bonding resulted from a sharing of electrons. In the formation of methane CH4 for example, carbon, electronic configuration l.s 2.s 2p. uses the tour electrons in the second quantum level to form four equivalent... 

Influence of the Fiber. In order for a dye to move from the aqueous dyebath to the fiber phase the combination of dye and fiber must be at a lower energy level than dye and water. This in turn implies that there is a more efficient, lower energy sharing of electrons or intramolecular energy forces, and there are a number of mechanisms that allow this to happen. 

The simplest example of covalent bonding is the hydrogen molecule. The proximity of the two nuclei creates a new electron orbital, shared by the two atoms, into which the two electrons go (Fig. 4.5). This sharing of electrons leads to a reduction in energy, and a stable bond, as Fig. 4.6 shows. The energy of a covalent bond is well described by the empirical equation... 

The idea put forth by G. N. Lewis in 1916 that chemical bonding results from a sharing of electron pairs between two atoms was a fundamental advance in bonding... 

The sharing of electrons can be shown by representing valence electrons as dots placed between the atoms ... 

Huggins, who has particularly emphasized the fact that different atomic radii are required for different crystals, has recently [Phys. Rev., 28, 1086 (1926)] suggested a set of atomic radii based upon his ideas of the location of electrons in crystals. These radii are essentially for use with crystals in which the atoms are bonded by the sharing of electron pairs, such as diamond, sphalerite, etc. but he also attempts to include the undoubtedly ionic fluorite and cesium chloride structures in this category. 

The sharing of electrons between carbon and hydrogen is an example of atom to-atom bonding known as covalency and the two-electron bond is called a covalent bond. 

While sharing of electrons, i.e., covalent bonding, is the major component of the cohesive force in intermetallics, rationalization of their structure formation based on such chemical bonding is not trivial, because of the failure of the common electron counting rules that chemists have developed over the years from the studies of covalent compounds. The origin of the problem is the well-delo-... 

The ionic model describes a number of metal halides, oxides, and sulfides, but it does not describe most other chemical substances adequately. Whereas substances such as CaO, NaCl, and M 2 behave like simple cations and anions held together by electrical attraction, substances such as CO, CI2, and HE do not. In a crystal of Mgp2, electrons have been transferred from magnesium atoms to fluorine atoms, but the stability of HE molecules arises from the sharing of electrons between hydrogen atoms and fluorine atoms. We describe electron sharing, which is central to molecular stability, in Chapters 9 and 10. 

Read the entire laboratory activity. Form a hypothesis about how to show sharing of electrons in a covalent bond in an illustration and in a model and how the type of bond is determined. Record your hypothesis on page 71. 

In contrast, covalent bonding involves the sharing of electron pairs between two specific atoms, and it is possible to speak of a definite bond. For example, in molecules of H, and CC14 there are one and four covalent bonds per molecule, respectively. 

The sharing of electrons fills the K shell for each hydrogen atom (2 electrons) and the L shell for the carbon atom (8 electrons). Opposite are two ways of showing how the atoms of the compound ethanol, C2Hr,OH (which is drinking alcohol), are connected to one another. Chemists usually use a dash to represent each pair of electrons shared between two atoms, instead of the dots used above. Each atom now has a filled outer shell. The hydrogens are each... 

An explanation of valency on the basis of modem views of atomic structure. It is assumed that certain arrangements of outer electrons in atoms ( octets or outer shells of eight electrons) are stable and tend to be formed by the transfer or sharing of electrons between atoms. See Covalency and Electrovalency. 

Based on the ionic radii, nine of the alkali halides should not have the sodium chloride structure. However, only three, CsCl, CsBr, and Csl, do not have the sodium chloride structure. This means that the hard sphere approach to ionic arrangement is inadequate. It should be mentioned that it does predict the correct arrangement of ions in the majority of cases. It is a guide, not an infallible rule. One of the factors that is not included is related to the fact that the electron clouds of ions have some ability to be deformed. This electronic polarizability leads to additional forces of the types that were discussed in the previous chapter. Distorting the electron cloud of an anion leads to part of its electron density being drawn toward the cations surrounding it. In essence, there is some sharing of electron density as a result. Thus the bond has become partially covalent. 

Ionic compounds are made up of positively charged ions (usually metal ions) and negatively charged ions (usually non-metal ions or polyatomic anions) held together by electrostatic forces of attraction. Molecular compounds are made up of discrete units called molecules. Generally they consist of a small number of nonmetal atoms held together by covalent bonds (sharing of electrons). 

The modem definition from IUPAC says, A covalent bond is a region of relatively high electron density between nuclei which arises (at least partially) from sharing of electrons, and gives rise to an attractive force and characteristic inter-nuclear distance . 

Bonding found within halogen molecule is covalent — formed as a result of sharing of electrons. 

Chemical bonds are classified into two groups transfer of electrons creates an ionic bond while the sharing of electrons leads to a covalent bond. Before studying chemical bonds we need to become familiar with their representation. Chemical bonds may be represented in several ways. We are going to study orbital representation, electron dot representation and line representation. Let s examine these three types using the example of the fluorine molecule, F2. 

Covalent bonding is the sharing of one or more pairs of electrons by two atoms. The covalent bonds in a molecule a covalently bonded compound are represented by a dash. Each dash is a shared pair of electrons. These covalent bonds may be single bonds, one pair of shared electrons as in H-H double bonds, two shared pairs of electrons as in H2C=CH2 or triple bonds, three shared pairs of electrons, N=N . It is the same driving force to form a covalent bond as an ionic bond—completion of the atom s octet. In the case of the covalent bond, the sharing of electrons leads to both atom utilizing the electrons towards their octet. 

Surface complexation models attempt to represent on a molecular level realistic surface complexes e.g., models attempt to distinguish between inner- or outer-sphere surface complexes, i.e., those that lose portions of or retain their primary hydration sheath, respectively, in forming surface complexes. The type of bonding is also used to characterize different types of surface complexes e.g., a distinction between coordinative (sharing of electrons) or ionic bonding is often made. While surface coordination complexes are always inner-sphere, ion-pair complexes can be either inner- or outer-sphere. Representing model analogues to surface complexes has two parts stoichiometry and closeness of approach of metal ion to... 

Throughout this book you have been studying traditional chemistry and chemical reactions. This has involved the transfer or sharing of electrons from the electron clouds, especially the valence electrons. Little has been said up to this point regarding the nucleus. Now we are going to shift our attention to nuclear reactions and, for the most part, ignore the electron clouds. 

The adsorption which results from the influence of van der Waals forces is essentially physical in nature. Because the forces are not strong, the adsorption may be easily reversed. In some systems, additional forces bind absorbed molecules to the solid surface. These are chemical in nature involving the exchange or sharing of electrons, or possibly molecules forming atoms or radicals. In such cases the term chemisorption is used to describe the phenomenon. This is less easily reversed than physical adsorption, and regeneration may be a problem. Chemisorption is restricted to just one layer of molecules on the surface, although it may be followed by additional layers of physically adsorbed molecules. 

Covalent bonds are strong bonds. Actual bonds are formed between the interacting molecules via the sharing of electrons. Hence, this type of interac-... 

Carbon-based molecules are constructed from atoms held together by the sharing of electron pairs these are arranged in space in precise ways. Some molecules are nonsuperimposable on their mirror images and are said to be chiral that is, they are handed. Chirality matters. 

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