Molecular orbitals electron clouds

Orbital Electron cloud, generated from a wave function, that represents the probability of locating an electron as a function of three-dimensional spatial coordinates. Orbitals can be atomic (AO) or molecular (MO), depending upon the region to which the electron is constrained. 

Hence we have two molecular orbitals, one along the line of centres, the other as two sausage-like clouds, called the n orbital or n bond (and the two electrons in it, the n electrons). The double bond is shorter than a single C—C bond because of the double overlap but the n electron cloud is easily attacked by other atoms, hence the reactivity of ethene compared with methane or ethane. 

H2, N2, or CO dissociates on a surface, we need to take two orbitals of the molecule into account, the highest occupied and the lowest unoccupied molecular orbital (the HOMO and LUMO of the so-called frontier orbital concept). Let us take a simple case to start with the molecule A2 with occupied bonding level a and unoccupied anti-bonding level a. We use jellium as the substrate metal and discuss the chemisorption of A2 in the resonant level model. What happens is that the two levels broaden because of the rather weak interaction with the free electron cloud of the metal. 

A measure of the ability of an atom within a molecule to attract bonding electrons toward itselP . For a bond between two atoms of different electronegativities, the electron molecular orbital cloud is not symmetric, and the atom with the higher electronegativity attracts the larger proportion of the cloud. The most popular quantitative description was presented by Pauling, who based his scale on bond dissociation energies (measured in kcal per mol). 

The greater the difference in electronegativity between two atoms, the more polar the bond is that forms between them. Imagine the electrons in the bond as being spread out into a cloud within the molecular orbital. In polar bonds, the cloud is denser in the vicinity of the more electronegative atom. In nonpolar bonds, like those formed between atoms of the Scime element, the cloud is evenly distributed between both atoms. Polar bonds have more ionic chciracter, whereas nonpolar bonds have more covalent character. Here s how to distinguish the chciracter of a bond ... 

As in the various atomic space orbitals, there are different geometries of electron clouds in the various molecular orbitals. 

A more refined description of dipole moments would also have to consider that lone pairs may also contribute to the molecular moment. This becomes important when the lone pairs are in directed nonspherical orbitals. In such cases, the center of negative charge in the electron cloud and the center of positive charge, the nucleus, do not coincide. The result... 

Torsional rotations around single and mulitple bonds are different processes. In a multiple bond a torsional rotation results in the transformation of one isomer into another. In contrast, rotation around single bonds leads to interconversion of conformed (Fig. 2.9). In the latter case, repulsion of the substituents is modeled by van der Waals interaction (see below) and the torsional potential describes the additional electronic component, including distortion of the molecular orbitals and repulsion by the electron clouds. 

The dipole moment of a compound is a function of the distribution of charge within the molecule, and appears to be a sensitive test for the accuracy of the compound s molecular wave functions. The dipole moment of a molecule can be approximated for a given direction as the sum of two components, /iq, the contribution from net charge densities on the atoms, and for each atom A, ftsp (A), an atomic polarization moment produced by the distortion of the electronic cloud around the atom. The atomic polarization moment results essentially from the mixture of s and p orbitals and, for a heteroatom, includes mv, the lone pair moment. 

Core electrons and electrons engaged in bonding are relatively tightly bound to the molecular nuclear framework. Lone-pair electrons or electrons in a (previously) virtual orbital, are relatively loosely held, and are on the average at a larger distance from the nuclei than core or bonding electrons. These expanded electron clouds... 

Ans. The six electrons occupy molecular orbitals, which are made by combining / -orbitals that are perpendicular to the plane of the molecule. The electron density can be shown by two identical circular clouds, one above and one below the plane of the molecule. 

These results imply that the electron density on the central carbon is higher than that on the terminal carbon.6 This makes no chemical sense and also disagrees with exact calculations. The error arises because we have ignored distortions of the molecular electron clouds. When the three-orbital correction term given in Equation (3.10) is added, VP2 becomes... 

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