Hybridization Examples- SP, SP2, SP3 Explained
What Hybridization Actually Is
Hybridization is how atoms rearrange their atomic orbitals to form new orbitals that point in specific directions. It's not some abstract concept—it's the reason molecules have the shapes they do.
The three main types you'll encounter are sp³, sp², and sp hybridization. Each one tells you something concrete about bond angles and molecular geometry.
SP³ Hybridization
When one s orbital mixes with three p orbitals, you get four equivalent sp³ orbitals. These orbitals point toward the corners of a tetrahedron.
Bond Angle and Geometry
The bond angle in sp³ hybridization is 109.5°. This is the tetrahedral angle. If you see bond angles around this value, you're probably looking at sp³ hybridization.
SP³ Hybridization Examples
Methane (CH₄) is the textbook example. Carbon has four bonds and no lone pairs. All four C-H bonds are equivalent. The geometry is perfectly tetrahedral.
Ethane (C₂H₆) works the same way. Each carbon in ethane is sp³ hybridized. The C-C bond is a sigma bond, and each carbon has three C-H bonds attached.
Water (H₂O) is sp³ hybridized, but it has two lone pairs. The hybridization still creates four sp³ orbitals—two hold bonding electrons, two hold lone pairs. This compresses the bond angle down to about 104.5°.
Ammonia (NH₃) follows the same pattern. Nitrogen uses sp³ orbitals: three for bonding, one for the lone pair. Bond angle is around 107°.
Key Point About SP³
Every atom with four electron groups and no double or triple bonds is sp³ hybridized. Count the regions of electron density, not just the bonds.
SP² Hybridization
Mix one s orbital with two p orbitals. You get three sp² orbitals in a trigonal planar arrangement. The leftover p orbital stays unhybridized and sits perpendicular to the plane.
Bond Angle and Geometry
The bond angle is approximately 120°. This is the trigonal planar angle. Any molecule with this geometry and double bonds is sp² hybridized.
SP² Hybridization Examples
Ethene (C₂H₄) is the classic case. Each carbon is sp² hybridized. The carbons form one sigma bond between them and two sigma bonds to hydrogens. The unhybridized p orbitals overlap sideways to form the pi bond in the double bond.
Boron trifluoride (BF₃) has boron sp² hybridized. Boron has three bonding domains and no lone pairs. The molecule is perfectly trigonal planar with 120° F-B-F angles.
Formaldehyde (H₂C=O) shows sp² hybridization at carbon and oxygen. The carbon is sp². The oxygen is also sp² hybridized—one orbital holds the lone pair, the other two form sigma bonds. The C=O double bond consists of one sigma and one pi bond.
Key Point About SP²
Any carbon involved in a double bond is sp² hybridized. The double bond means one sigma bond (from sp²) plus one pi bond (from the leftover p orbital).
SP Hybridization
Mix one s orbital with one p orbital. You get two sp orbitals pointing in opposite directions—linear geometry. Two p orbitals remain unhybridized.
Bond Angle and Geometry
The bond angle is 180°. Linear geometry. If you see a triple bond or two double bonds on a central atom, you're looking at sp hybridization.
SP Hybridization Examples
Acetylene (C₂H₂) has both carbons sp hybridized. Each carbon forms one sigma bond to hydrogen and one sigma bond to the other carbon. The C≡C triple bond consists of one sigma bond plus two pi bonds from the two unhybridized p orbitals on each carbon.
Carbon dioxide (CO₂) is sp hybridized at carbon. The carbon forms two double bonds to oxygen. Each C=O bond is one sigma (sp orbital) and one pi (p orbital). The molecule is linear.
BeCl₂ (beryllium chloride in gas phase) is sp hybridized. Beryllium forms two sigma bonds with no lone pairs. Linear geometry at 180°.
Key Point About SP
Two regions of electron density with no lone pairs on the central atom = sp hybridization. Triple bonds count as one region. Two double bonds count as one region.
Hybridization Comparison Table
| Hybridization | Atomic Orbitals Mixed | Number of Hybrid Orbitals | Geometry | Bond Angle | Unhybridized p Orbitals |
|---|---|---|---|---|---|
| sp³ | 1 s + 3 p | 4 | Tetrahedral | 109.5° | 0 |
| sp² | 1 s + 2 p | 3 | Trigonal Planar | 120° | 1 |
| sp | 1 s + 1 p | 2 | Linear | 180° | 2 |
How to Determine Hybridization: Step by Step
Here's how you actually figure out which hybridization applies to a given atom.
Step 1: Draw the Lewis Structure
You need to see the electron pairs, bonds, and lone pairs around the atom in question. Without the Lewis structure, you're guessing.
Step 2: Count the Steric Number
The steric number equals the number of sigma bonds plus the number of lone pairs on that atom.
- Steric number 4 → sp³ hybridization
- Steric number 3 → sp² hybridization
- Steric number 2 → sp hybridization
Step 3: Check for Multiple Bonds
Double bonds and triple bonds don't change the steric number. A carbon in a C=C double bond still has steric number 3 (three sigma bonds: one to the other carbon, two to hydrogens). That's why it's sp², not sp³.
Step 4: Verify the Geometry
Match the bond angles to what you'd expect. If you calculate sp² but see 180° bond angles, something's wrong with your structure.
Quick Examples Walkthrough
Example 1: SO₂
Sulfur in SO₂ has three electron regions: two bonds and one lone pair. Steric number = 3. Hybridization is sp². The molecule is bent, not trigonal planar, because the lone pair pushes the bonded atoms down.
Example 2: Ethylene glycol (HO-CH₂-CH₂-OH)
Each carbon has four bonds and no lone pairs. All four bonds are sigma bonds. Steric number = 4. Both carbons are sp³ hybridized. The oxygens are also sp³ hybridized—one lone pair on each.
Example 3: Acetonitrile (CH₃-C≡N)
The carbon attached to the triple bond (the nitrile carbon) has two electron regions: one sigma bond to the methyl carbon and one sigma bond to nitrogen. Steric number = 2. That's sp hybridization. The C-C bond is a single sigma bond. The C≡N bond is one sigma and two pi bonds.
What About Nitrogen and Oxygen?
Hybridization rules apply to all atoms, not just carbon. Nitrogen with three bonds and one lone pair is sp³. Nitrogen in a double bond (like in imines) is sp². Nitrogen with a triple bond (like in nitriles) is sp.
Oxygen with two bonds and two lone pairs is sp³. Oxygen in a carbonyl (C=O) is sp² hybridized—one lone pair in an sp² orbital, one sigma bond to carbon, one sigma bond to nothing (wait, no—carbonyl oxygen has two lone pairs and forms one sigma bond to carbon, so steric number is 3).
Common Mistakes to Avoid
- Don't count pi bonds when determining steric number. Only sigma bonds and lone pairs matter.
- Don't assume carbon is always sp³. Check the bonds first.
- Lone pairs count toward steric number even though they're invisible in the geometry.
- Bond angle deviations are normal. Lone pairs compress angles; multiple bonds slightly expand them.
The Bottom Line
Hybridization isn't complicated once you stop overthinking it. Count electron regions, match to the steric number, check the geometry. sp³ means four regions (tetrahedral). sp² means three regions with one leftover p orbital (trigonal planar). sp means two regions with two leftover p orbitals (linear). That's the whole system.
Work through enough examples and you'll stop needing to think about it at all. It'll be automatic.