MO description of bonding in the Lewis-valent compounds

In order to describe the Lewis-valent compounds, EH2, E(CH3)2 or ECI2, in terms of 2c, 2e bonds, we must form appropriate hybrid orbitals on the central atom E pointing towards the two ligating atoms. Each of these hybrids may then be combined with an appropriate orbital on the ligating atom to form a 2c MO which accommodates two electrons. 

The two nonbonding electron pairs may be described in two ways. We may choose to accommodate two electrons in a third hybrid orbital h3 with maximum electron density in the plane of the molecule corresponding to the /i3 hybrid orbital defined by equation (13.5) and the last two electrons in an uhybridized p orbital perpendicular to the molecular plane. The other possibility is to combine hs and p to form two new equivalent hybrids, and hs pointing in approximately tetrahedral directions  

See Fig. 17.3. The total electron density calculated for the electron configuration h hl is identical to the electron density calculated for the electron configuration the states 

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