Sp3

Sp3 refers to a type of atomic orbital hybridization in which one s orbital and three p orbitals on the same atom mix to form four equivalent sp3 hybrid orbitals. These hybrids are arranged in a tetrahedral geometry, with an ideal bond angle of 109.5 degrees between them. Sp3 hybridization is commonly invoked for main-group elements, especially carbon, when forming single bonds.

In carbon compounds, sp3 describes carbon in saturated frameworks. The four sp3 hybrids form sigma bonds to hydrogen or other carbon atoms, as seen in methane (CH4) and ethane (C2H6). The geometry is roughly tetrahedral, and there are no unhybridized p orbitals to participate in pi bonding under standard valence bond treatment.

Molecules with lone pairs on the central atom are also described using sp3. Ammonia (NH3) has three N–H sigma bonds and one lone pair occupying an sp3 set, giving a trigonal pyramidal shape. Water (H2O) has two bonds and two lone pairs, resulting in a bent shape. Real-world bond angles deviate from 109.5 degrees due to lone-pair repulsion.

Sp3 is contrasted with sp2 and sp hybridizations. Sp2 uses one s and two p orbitals to make three sp2 hybrids suitable for trigonal planar geometry and pi bonding; sp uses one s and one p to form two linear sp orbitals. Sp3 is most appropriate for saturated, single-bonded systems, though excited or ionic states can involve different hybrid descriptions.