Valence shell of carbon

Free radical (Section 4 16) Neutral species in which one of the electrons in the valence shell of carbon is unpaired An ex ample is methyl radical CH3... 

The use of resonance structures such as 7 and 8 to describe bond polarity led to a subtle change in the meaning of the octet rule, namely, that an atom obeys the octet rule if it does not have more than eight electrons in its valence shell. As a result, resonance structures such as 7 and 8 are considered to be consistent with the octet rule. However, this is not the sense in which Lewis used the octet rule. According to Lewis, a structure such as 7 would not obey the octet rule because there are only three pairs of electrons in the valence shell of carbon, just as BF3 does not obey the octet rule for the same reason. Clearly the octet rule as defined by Lewis is not valid for hypervalent molecules, which do, indeed, have more than four pairs of shared electrons in the valence shell of the central atom. 

In this way, repulsions between electrons associated with completion of the valence shell of carbon are compensated by the electron-attracting powers of the positively charged nuclei of the atoms to which the carbon is bonded. 

What are some of the pitfalls of this method If only a single electron pair in 1-17 is moved, 1-19 is obtained. However, this structure does not make sense. At the carbon labeled 1, there are five bonds to carbon this is a carbon with 10 electrons. However, it is not possible to expand the valence shell of carbon. Similar rearrangement of other ir bonds in either 1-16, 1-17, or 1-18 would lead to similarly nonsensical structures. 

There are four electrons in the valence shell of carbon, so in order to achieve an octet it requires four more. The shape of the s atomic orbital is spherical, while... 

Next, we will look at the Lewis dot diagram for carbon, which has an electron configuration of Is2 2sz 2p2. The valence shell of carbon contains a total of four electrons (2s2 2p2), so our dot diagram will show four dots. The two s electrons will go on the left-hand side of the elemental notation, but the two p electrons will split up, one per side, according to Hund s Rule. 

Akiba and coworkers have established the existence of hexacoordinate hypervalent compounds, that is, 12-C-6 species with 12 formally assignable electrons in the valence shell of carbon with six ligands (substituents). In 12-C-6 compounds, carbon is sp hybridized, bears two positive charges, and attracts four nucleophiles to form two 3c-Ae bonds. Geometry optimization at the B3LYP/cc-pVDZ level has been performed, with dications having the... 

Problem 3,23. In Problem 3.18, methane, with the composition CH4, was shown to have a three-dimensional structure known as a tetrahedron. We know that the valence shell of carbon consists of four electrons in two different kinds of orbitals, 2s and 2p orbitals. Knowing this, how can we explain the fact that carbon forms four equivalent covalent bonds, bonds of identical character, with the Is electrons of hydrogen ... 

The components of the valence shell of carbon being a scalar (2s) and a vector (2p), the tetrahedron is the optimal geometry that provides four valence sites, which together transform precisely as scalar and vector. The alternative high-symmetry... 

STEP 2 Reaction of an electrophile and a nucleophile to form a new covalent bond. The reaction of the sec-butyl cation (an electrophile and a Lewis acid) with chloride ion (a nucleophile and a Lewis base) completes the valence shell of carbon and gives 2-chlorobutane ... 

Reaction of the sec-butyl cation (an electrophile) with bromide ion (a nucleophile) completes the valence shell of carbon and gives 2-bromobutane. 

Carbon has six electrons, two in the Is orbital, and four valence electrons that occupy the 2s and 2p valence orbitals. Based on the rules briefly reviewed here, the lowest energy electronic diagram of the valence shell of carbon is as shown in the margin. 

If we try to extend the unmodified valence bond method of Section 11-2 to a greater number of molecules, we are quickly disappointed. In most cases, our descriptions of molecular geometry based on the simple overlap of unmodified atomic orbitals do not conform to observed measurements. For example, based on the ground-state electron configuration of the valence shell of carbon... 

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