In atoms with electrons in more than one orbital, some hybridization or mixing of the orbitals may occur. If all four orbitals (1 s and 3 p) are needed for bonding, they will hybridize to form four identical orbitals. Hybridizing 1 s and 2 p orbitals yields three identical orbitals. Since there are only three orbitals involved with this hybridization, one p orbital remains unchanged. An sp hybridized orbital is the combination of the s orbital and 1 p orbital, leaving 2 p orbitals unchanged.
Since the electrons of an atom all have an equal negative charge, the electrons repel each other. Hybridization of the orbitals maximizes the separation distance of the electrons and thus lowers the energy of the molecule.
