Shared electron

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. 

In each of the examples given so far each element has achieved a noble gas configuration as a result of electron sharing. There are. however, many examples of stable covalent compounds in which noble gas configurations are not achieved, or are exceeded. In the compounds of aluminium, phosphorus and sulphur, shown below, the central atoms have 6. 10 and 12 electrons respectively involved in bondinc... 

Another way of constructing wave functions for open-shell molecules is the restricted open shell Hartree-Fock method (ROHF). In this method, the paired electrons share the same spatial orbital thus, there is no spin contamination. The ROHF technique is more difficult to implement than UHF and may require slightly more CPU time to execute. ROHF is primarily used for cases where spin contamination is large using UHF. 

The structure shown is the best (most stable) Lewis structure for methyl nitrite All atoms except hydro gen have eight electrons (shared + unshared) in their valence shell... 

The UHE wave function can also apply to singlet molecules. Usually, the results are the same as for the faster RHEmethod. That is, electrons prefer to pair, with an alpha electron sharing a molecular space orbital with a beta electron. Use the UHE method for singlet states only to avoid potential energy discontinuities when a covalent bond is broken and electrons can unpair (see Bond Breaking on page 46). 

In the early part of the twentieth century, G. N. Lewis observed that chemical bonding seemed to favor a state in which the atoms in stable compounds, by sharing electrons, achieved the stable electron distribution exhibited by the nonreactive noble gases, so-called because they are almost always found as pure elements in the gas state. He proposed that the electrons shared between two elements act as an electromagnetic glue to hold the two atoms together. The positive nuclei are attracted to the negative electrons the electrons spend most of their... 

How does electron sharing lead to bonding between atoms Two models have been developed to describe covalent bonding valence bond theory and molecular orbital theory. Each model has its strengths and weaknesses, and chemists tend... 

We said in Section 1.5 that chemists use two models for describing covalent bonds valence bond theory and molecular orbital theory. Having now seen the valence bond approach, which uses hybrid atomic orbitals to account for geometry and assumes the overlap of atomic orbitals to account for electron sharing, let s look briefly at the molecular orbital approach to bonding. We ll return to the topic in Chapters 14 and 15 for a more in-depth discussion. 

A covalent bond is formed when an electron pair is shared between atoms. According to valence bond theory, electron sharing occurs by overlap of two atomic orbitals. According to molecular orbital (MO) theory, bonds result from the mathematical combination of atomic orbitals to give molecular orbitals, which belong to the entire molecule. Bonds that have a circular cross-section and are formed by head-on interaction are called sigma (cr) bonds bonds formed by sideways interaction ot p orbitals are called pi (77-) bonds. 

A pair of electrons shared between two atoms is a covalent bond, ordinarily shown as a straight line between bonded atoms. 

Single bond A pair of electrons shared between two bonded atoms, 167 Six-coordinate metal complex, 413-414 Skeleton structure A structure of a species in which only sigma bonds are shown, 168... 

Now we have the compound H 0. By either representation, the bonding capacity of oxygen is expended when two bonds are formed. Oxygen is said to be divalent, and the compound H 0 is extremely stable. Each of the atoms in H 0 has filled its valence orbitals by electron sharing. 

All chemical bonds occur because electrons can be placed simultaneously near two nuclei. Yet it is often true that the electron-sharing which permits this is not exactly equal sharing. Sometimes the electrons, though close to both nuclei, tend to distribute nearer to one nucleus... 

The representation (56) shows two pairs of electrons shared. Each oxygen atom finds itself near eight electrons. There is, on the one hand, a stable molecule, because all of the bonding capacity of each oxygen atom is in use. On the other hand, this special aspect of the bonding of oxygen undoubtedly contributes to the reactivity of oxygen. 

When drawing a box diagram, show the electrons in different orbitals of the same subshell with parallel spins electrons sharing an orbital have paired spins. 

As will become apparent as this chapter progresses, many of our basic ideas on the chemical bond were proposed by Ci. N. Lewis, one of the greatest of all chemists, in the early years of the twentieth century. Lewis devised a simple way to keep track of valence electrons when atoms form ionic bonds. He represented each valence electron as a dot and arranged the dots around the symbol of the element. A single dot represents an electron alone in an orbital a pair of dots represents two paired electrons sharing an orbital. Examples of the Lewis symbols of atoms are... 

Because nonmetals do not form monatomic cations, the nature of bonds between atoms of nonmetals puzzled scientists until 1916, when Lewis published his explanation. With brilliant insight, and before anyone knew about quantum mechanics or orbitals, Lewis proposed that a covalent bond is a pair of electrons shared between two atoms (3). The rest of this chapter and the next develop Lewis s vision of the covalent bond. In this chapter, we consider the types, numbers, and properties of bonds that can be formed by sharing pairs of electrons. In Chapter 3, we revisit Lewis s concept and see how to understand it in terms of orbitals. 

The bond in a heteronuclear diatomic molecule, a diatomic molecule built from atoms of two different elements, is polar, with the electrons shared unequally by the two atoms. We therefore rewrite Eq. I as... 

De Broglie received the Nobel Prize in physics in 1929, only two years after experiments confirmed his theory. Davisson, a student of Nobel laureate Robert Millikan, and Thomson, the son and student of J. J. Thomson (who won the Nobel prize for discovering the electron), shared the Nobel Prize in physics in 1937. 

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. 

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