sp3 Hybridization
sp³ hybridization occurs when one s orbital and three p orbitals of the same atom mix to form four equivalent sp³ hybrid orbitals, each oriented at approximately 109.5° from one another in a tetrahedral arrangement. This type of hybridization is exhibited by carbon in saturated compounds like methane (CH₄), by nitrogen in ammonia (NH₃), and by oxygen in water (H₂O), though the presence of lone pairs in NH₃ and H₂O slightly distorts the ideal tetrahedral angle. sp³ hybridization is fundamental to understanding the three-dimensional structure of organic molecules, including all alkanes and the carbon backbone of biological macromolecules.
Key Formula
sp3 = (1/2)(s + px + py + pz)
LaTeX: \text{sp}^3 = \frac{1}{2}(s + p_x + p_y + p_z)
| Symbol | Meaning | Unit |
|---|---|---|
| s | 2s atomic orbital contribution | dimensionless |
| p_x, p_y, p_z | 2p atomic orbital contributions along x, y, z axes | dimensionless |
| sp³ | Resulting hybrid orbital (one of four equivalent orbitals) | dimensionless |
Worked Example
Problem
Describe the sp³ hybridization of carbon in methane (CH₄). How many sigma bonds are formed, and what are the bond angles?
Solution
Step 1: Ground state carbon electron configuration: 1s² 2s² 2p². Only 2 unpaired electrons — would form only 2 bonds. Step 2: Promotion: 1 electron from 2s moves to empty 2p orbital → 1s² 2s¹ 2p³ (4 unpaired electrons). Step 3: Hybridization: 1 s orbital + 3 p orbitals combine to form 4 sp³ hybrid orbitals of equal energy. Step 4: Each of the 4 sp³ orbitals overlaps with 1s orbital of hydrogen to form 4 C–H sigma (σ) bonds. Step 5: The 4 sp³ orbitals point toward the corners of a tetrahedron → bond angles = 109.5°. Step 6: Methane has 4 equivalent C–H bonds, tetrahedral geometry, no lone pairs, nonpolar molecule.
Answer
Carbon in CH₄ is sp³ hybridized: 4 σ bonds, tetrahedral geometry, all H–C–H bond angles = 109.5°.
sp³ Hybridized Molecules: Geometry and Bond Angle Comparison
| Molecule | Central Atom | Bonding Pairs | Lone Pairs | Bond Angle |
|---|---|---|---|---|
| Methane (CH₄) | C | 4 | 0 | 109.5° |
| Ammonia (NH₃) | N | 3 | 1 | 107.0° |
| Water (H₂O) | O | 2 | 2 | 104.5° |
| Ethane (C₂H₆) | C (each) | 4 | 0 | 109.5° |
| Chloromethane (CH₃Cl) | C | 4 | 0 | ≈109.5° |
| Phosphine (PH₃) | P | 3 | 1 | 93.5° |
Interactive Tools
Wikimedia Commons, CC BY-SA
Related Terms
Hybridization
Hybridization is a theoretical concept in chemistry describing the mixing of atomic orbitals of similar energy within the same atom to form new hybrid orbitals of equivalent energy and shape, oriented to minimize electron repulsion. Developed by Linus Pauling in 1931, hybridization explains molecular geometry that cannot be accounted for by simple orbital overlap — for example, carbon's four equivalent C–H bonds in methane despite having distinct 2s and 2p orbitals. The type of hybridization (sp, sp², sp³, sp³d, sp³d²) determines bond angles, molecular geometry, and the presence of pi bonds.
Molecular Geometry
Molecular geometry (or molecular shape) refers to the three-dimensional spatial arrangement of atoms within a molecule, determined by the positions of the atoms — not the lone pairs — around the central atom. The geometry is predicted using VSEPR theory or hybridization models and directly influences physical properties such as polarity, reactivity, phase of matter, colour, magnetism, and biological activity. Common geometries include linear, bent, trigonal planar, trigonal pyramidal, tetrahedral, and octahedral.
VSEPR Theory
Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the three-dimensional geometry of molecules based on the principle that electron pairs in the valence shell of a central atom repel each other and arrange themselves as far apart as possible to minimize repulsion. The theory considers both bonding pairs and lone pairs, with lone pairs exerting greater repulsive force than bonding pairs, which distorts ideal bond angles. VSEPR theory was developed by Ronald Gillespie and Ronald Nyholm in 1957 and remains one of the most useful and accessible tools for predicting molecular shape.
The notation "sp³" denotes the mixing of one s orbital and three p orbitals (superscript 3). The concept derives from Linus Pauling's 1931 valence bond theory, where "hybridization" described orbital combination to explain molecular geometry.