Molecular orbitals antibonding defined

Define the following terms bonding molecular orbital, antibonding molecular orbital, pi molecular orbital, sigma molecular orbital. 

At first sight, the molecular orbital description of N2 looks quite different from the Lewis description ( N=N ). However, it is, in fact, very closely related. We can see their similarity by defining the bond order (b) in molecular orbital theory as the net number of bonds, allowing for the cancellation of bonds by antibonds ... 

All the atoms of butadiene lie in a plane defined by the s p hybrid orbitals. Each carbon atom has one remaining p orbital that points perpendicular to the plane, in perfect position for side-by-side overlap. Figure 10-42 shows that all four p orbitals interact to form four delocalized molecular orbitals two are bonding MOs and two are antibonding. The four remaining valence electrons fill the orbitals, leaving the two p orbitals empty. 

Defined as N = (n - n )/2, where n and n are the numbers of electrons in the bonding and antibonding molecular orbitals, respectively, of the corresponding dioxygen species. e R = alkyl. 

Bond Order It is defined as half of the difference between number of electrons in bonding and antibonding molecular orbitals. 

Earlier in this chapter, you learned the definition of bond order in the valence bond theory. In molecular orbital theory, the bond order is defined as one-half the difference between the number of electrons in bonding orbitals and the number of electrons in antibonding orbitals. Mathematically, this can be expressed as... 

These functions account for 15 electrons (10 in the bonding and 5 in the antibonding orbitals), while the remaining 38 valence electrons occupy the multipole functions of the b part. The five B electrons are responsible for the bond polarization, as the 10 a electrons in the M.O s equally occupy bonding and antibonding orbitals and give neither spin nor charge transfer. The molecular orbitals i ) are defined in Table VI. 

We must now look at the coefficients, c, of equation 2-1. When there are electrons in the orbital, the squares of the c-values are a measure of the electron population in the neighbourhood of the atom in question. Thus in each orbital the sum of the squares of all the c-values must equal one, since only one electron in each spin state can be in the orbital. Now the orbitals in hydrogen are symmetric about the mid-point of the H—H bond in other words c2 must equal c2. Thus we have defined what the values of c, and c2 in the bonding orbital must be, namely 1/ /2 = 0-707. If all molecular orbitals were filled, then there would have to be one electron in each spin state on each atom, and this gives rise to a second criterion for c-values, namely that the sum of the squares of all the c-values on any one atom in all the molecular orbitals must also equal one. Thus the antibonding orbital of hydrogen, [Pg.7]

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