Ground state electron configurations, homonuclear

Table 6.3. Ground state electron configurations and states for homonuclear diatomic molecules in the first row of the periodic table...

We are now ready to study the ground-state electron configuration of molecules containing second-period elements. We will consider only the simplest case, that of homonuclear diatomic molecules, or diatomic molecules containing atoms of the same elements. 

Fig. 2.9 Changes in the energy levels of the MOs and the ground state electronic configurations of homonuclear diatomic molecules involving first-row p-block elements.

Table 20.2 Ground-State Electron Configurations of Homonuclear Diatomic Molecules...

Give the term symbol for the ground-state electron configuration of each of the second-row homonuclear diatomic molecules (Li2 through F2). 

Because both electrons reside in the a bonding orbital, an electron configuration of can be used to describe the ground electronic state of H2. (Because H2 is a homonuclear diatomic molecule, we add a subscript g to the label——to indicate the orbital s symmetry property with respect to the center of the molecule. Electrons in the antibonding orbital are labeled a, the u also referring to the orbital s symmetry properties. Symmetry will be discussed in the next chapter.) To emphasize that the electrons in the a orbital derive from Is electrons from H atoms, the more detailed (cTgls) label can also be used. 

For homonuclear diatomic molecules with more than four electrons, we require additional molecular orbitals beyond the erg 1 and a 1 orbitals. For U2 and Be2 we can use the <7g2j and the cr 2 orbitals in Eq. (20.2-9) and Eq. (20.2-10). The electron configuration of Li2 in the ground state is... 

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