What Is Orbital Hybridization?
Orbital hybridization is the mixing of an atom's atomic orbitals (like s and p) into new, equivalent hybrid orbitals that better explain molecular geometry and bonding. It's why carbon can form four identical bonds in methane even though its unhybridized orbitals aren't identical. The type of hybridization — sp, sp², or sp³ — is found from the steric number, the sum of sigma bonds and lone pairs around the central atom.
Orbital hybridization is the blending of atomic orbitals to form new hybrid orbitals of equal energy and shape; the type is determined by the steric number (sigma bonds + lone pairs): 2 → sp (linear), 3 → sp² (trigonal planar), 4 → sp³ (tetrahedral).
- 1↓Count sigma bondsCount every single bond and every one sigma bond within a double or triple bond around the central atom.
- 2↓Count lone pairsCount the nonbonding electron pairs sitting directly on the central atom (from its Lewis structure).
- 3↓Add for steric numberSteric number = sigma bonds + lone pairs; this total tells you how many hybrid orbitals are needed.
- 4Match to hybridization type2 → sp (linear), 3 → sp² (trigonal planar), 4 → sp³ (tetrahedral), 5 → sp³d, 6 → sp³d².
Try it: interactive calculator
Step-by-step worked examples
Determine the hybridization of the central carbon in methane, CH₄.
Carbon forms 4 single (sigma) bonds to hydrogen and has 0 lone pairs. Steric number = 4 (bonds) + 0 (lone pairs) = 4. A steric number of 4 corresponds to sp³ hybridization — a tetrahedral shape (109.5° bond angles).
Determine the hybridization of the central carbon in carbon dioxide, CO₂.
Carbon forms 2 sigma bonds (one to each oxygen, even though each is a double bond, only one is a sigma bond) and has 0 lone pairs. Steric number = 2 (sigma bonds) + 0 (lone pairs) = 2. A steric number of 2 corresponds to sp hybridization — a linear shape (180° bond angle).
Determine the hybridization of the central nitrogen in ammonia, NH₃.
Nitrogen forms 3 sigma bonds to hydrogen and has 1 lone pair. Steric number = 3 (bonds) + 1 (lone pair) = 4. A steric number of 4 corresponds to sp³ hybridization — the electron geometry is tetrahedral, though the molecular shape is trigonal pyramidal due to the lone pair.
Flashcards
Quick quiz
Q1.What is the hybridization of the central atom with 4 sigma bonds and 0 lone pairs?
Q2.What is the steric number of the oxygen in water, H₂O (2 sigma bonds, 2 lone pairs)?
Q3.Which hybridization corresponds to a linear molecular geometry?
Q4.In a C=C double bond, how many sigma bonds does that double bond contribute to the steric number?
The full card deck, worked steps and AI-tutor support for “What Is Orbital Hybridization?” are in Notek — study by hand before your exam.
Common mistakes
Counting a double bond as 2 toward the steric number. — Correct: A double bond is only 1 sigma bond (plus 1 pi bond); it contributes just 1 to the steric number.
Forgetting to count lone pairs on the central atom. — Correct: Lone pairs occupy hybrid orbitals just like bonds do, so they must be added to the steric number.
Assuming molecular shape and electron geometry are always the same. — Correct: They match only when there are no lone pairs; with lone pairs, the molecular shape (e.g., trigonal pyramidal for NH₃) differs from the electron geometry (tetrahedral).
Thinking hybridization only applies to carbon. — Correct: Any central atom with bonding and lone pairs (N, O, S, P, etc.) can be hybridized — not just carbon.
FAQ
What is orbital hybridization?
The mixing of atomic orbitals (s, p, sometimes d) into new hybrid orbitals of equal energy and shape, used to explain molecular bonding and geometry.
What is the hybridization formula?
Steric number = sigma bonds + lone pairs; 2=sp, 3=sp², 4=sp³, 5=sp³d, 6=sp³d².
What are examples of hybridization?
CH₄ is sp³ (tetrahedral), CO₂ is sp (linear), and BF₃ is sp² (trigonal planar).
How do you calculate hybridization for a molecule?
Draw the Lewis structure, count sigma bonds and lone pairs on the central atom, add them for the steric number, then match it to sp/sp²/sp³/etc.