The hybridization of Be in BeH2 can be understood using valence bond theory. In this theory, the atomic orbitals of the participating atoms combine to form hybrid orbitals that have the appropriate symmetry to overlap with the orbitals of the other atoms and form chemical bonds.
In the case of BeH2, the beryllium atom has two valence electrons, one in the 2s orbital and one in the 2p orbital. The 2s orbital is spherical in shape, while the 2p orbital is dumbbell-shaped with lobes oriented along the x, y, and z axes.
When BeH2 forms, the 2s and 2p orbitals of beryllium hybridize to form two sp hybrid orbitals. These sp hybrid orbitals are directed in a linear fashion, with an angle of 180 degrees between them. This linear arrangement of the sp hybrid orbitals allows for optimal overlap with the 1s orbitals of the two hydrogen atoms.
The overlap of the sp hybrid orbitals of beryllium with the 1s orbitals of hydrogen results in the formation of two Be-H bonds. These bonds are covalent in nature, meaning that they are formed by the sharing of electrons between the beryllium and hydrogen atoms.
In summary, the hybridization of Be in BeH2 is sp, which results in the formation of two equivalent sp hybrid orbitals that overlap with the 1s orbitals of the two hydrogen atoms to form two Be-H bonds.
