Beryllium hydride hybrid orbitals

The figure depicts the electron clouds in a complete beryllium hydride molecule. Notice that the hydrogen Is orbitals are not hybridized here they are still spherical. The two bonds in beryllium hydride are the regions of overlap between the hydrogen 7s and beryllium sp hybrid orbitals. 

Draw the Lewis structure for beryllium hydride, BeH2. Draw the orbitals that overlap in the bonding of BeH2, and label the hybridization of each orbital. Predict the H—Be — H bond angle. 

Even though the valence would be correct after promotion, the structure still would be wrong. Beryllium hydride would have two different kinds of bonds, and methane would have three identical bonds formed by overlap of H(ls) with the C(2p) orbitals and a different bond formed by H(ls) and C(2s). Pauling proposed that new orbitals with the proper symmetry for bond formation could be formed by hybridization of 2s and 2p orbitals after promotion. The Be(2s) and Be(2pz) orbitals would combine to form two equivalent hybrid orbitals oriented 180° apart. The C(2s) would hybridize with the three C 2p) orbitals to give four equivalent new orbitals in a tetrahedral arrangement around the carbon atom. 

Beryllium hydride is formed in a similar fashion. Here the overlap is between the sp hybrid orbitals of the beryllium atom and the partly filled Is orbital from each of two hydrogen atoms, to give two covalent bonds. 

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