Sp2d hybrid orbitals

M is sp2d-hybridized The four hybrids carried by the metal point into four directions, in the same plane. It is impossible to obtain an alignment of the sp -hybrids of oxygens that point in directions separated by angles of 109.5 . Consequently, the packing will be obtained from bent orbitals. The lattice will be compressed (quadratic system). 

In CuO, the sp2d hybridization leaves five atomic orbitals unused. Nine electrons per copper atom are available CuO is a black semi--conductor. 

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