Hybridization Calculator
Determine sp, sp2, sp3, sp3d, or sp3d2 hybridization from steric number (bonds + lone pairs).
What Hybridization Actually Describes
An isolated carbon atom has two electrons in a spherical 2s orbital and two in dumbbell-shaped 2p orbitals. Those orbitals point in the wrong directions and have the wrong energies to explain methane's four identical bonds at 109.5°. Hybridization is the model that resolves this: the atomic orbitals mix to form new equivalent orbitals aimed where the bonds actually are.
The bookkeeping is straightforward. Count the steric number — sigma bonds plus lone pairs — and that tells you how many orbitals must be mixed. Four regions means four hybrid orbitals, made from one s and three p orbitals, giving sp3. Three regions needs only three, so one p orbital is left unhybridized and remains available for pi bonding.
| Steric number | Hybridization | Orbitals mixed | Geometry | Unhybridized p left |
|---|---|---|---|---|
| 2 | sp | 1s + 1p | Linear, 180° | 2 (for two pi bonds) |
| 3 | sp2 | 1s + 2p | Trigonal planar, 120° | 1 (for one pi bond) |
| 4 | sp3 | 1s + 3p | Tetrahedral, 109.5° | 0 |
| 5 | sp3d | 1s + 3p + 1d | Trigonal bipyramidal | 0 |
| 6 | sp3d2 | 1s + 3p + 2d | Octahedral, 90° | 0 |
The leftover p orbitals matter enormously. In ethylene each carbon is sp2 with one unhybridized p orbital, and those two p orbitals overlap sideways to form the pi bond. That pi bond is what prevents rotation about a C=C double bond — rotating would break the sideways overlap — which is why cis and trans isomers exist at all.
Note the direction of reasoning: geometry determines hybridization, not the other way round. Hybridization is a description fitted to observed shape, not a force that causes it.
Worked Examples
Common Mistakes
Only sigma bonds and lone pairs count. A double bond contributes one sigma bond and one pi bond, so it adds one to the steric number, not two.
Lone pairs occupy hybrid orbitals just as bonds do. Oxygen in water has two bonds plus two lone pairs, giving steric number 4 and sp3 hybridization — not sp.
Hydrogen has only a 1s orbital with nothing to mix it with, so it is never hybridized. Hybridization applies to the central atom.
The involvement of d orbitals in main-group bonding is disputed, and modern treatments often explain hypervalent molecules through three-centre four-electron bonding instead. The sp3d label remains a useful teaching shorthand.
Frequently Asked Questions
Formula Explorer connections
Interpretation: This relationship uses electronic structure, bonding or molecular geometry to predict a chemical property or structural descriptor. Assumption: The model may be an approximation; resonance, solvent, coordination environment, conformation and experimental conditions can affect real molecules.