What is Hybridization? sp, sp², sp³
Hybridization is the mixing of atomic orbitals (s, p, d) to create hybrid orbitals that point toward bonding partners. The type of hybridization (sp, sp², sp³) determines the molecular geometry and bond angles around an atom.
Hybridization is the blending of s and p orbitals to form hybrid orbitals suited for bonding. sp hybridisation gives linear geometry (180°); sp² gives trigonal-planar (120°); sp³ gives tetrahedral (109.5°).
- •Geometry: Linear (180°)
- •Orbitals mixed: 1 s + 1 p
- •Hybrid orbitals: 2
- •Example: CO₂, HCN, BeH₂
- •Geometry: Trigonal-planar (120°)
- •Orbitals mixed: 1 s + 2 p
- •Hybrid orbitals: 3
- •Example: BF₃, C₂H₄, NO₃⁻
Step-by-step worked examples
What is the hybridisation of carbon in CH₄ and what geometry does it adopt?
Carbon has 4 valence electrons; forms 4 C–H bonds Carbon needs 4 hybrid orbitals → sp³ hybridisation (1 s + 3 p mixed) sp³ orbitals point tetrahedral → 4 hybrid orbitals, 109.5° angles Geometry: Tetrahedral
Determine the hybridisation of nitrogen in NH₃.
Nitrogen: 5 valence electrons; forms 3 N–H bonds + 1 lone pair Needs 4 hybrid orbitals → sp³ hybridisation 4 sp³ orbitals at 109.5°; one holds a lone pair Geometry: Trigonal pyramidal (bond angles compressed to 107° by lone pair repulsion)
What is the hybridisation and geometry of carbon in C₂H₄ (ethene)?
Each carbon forms 3 σ bonds (1 C–C + 2 C–H) + 1 π bond 3 σ bonds need 3 hybrid orbitals → sp² hybridisation sp² orbitals at 120° angles Geometry: Trigonal planar around each carbon
Flashcards
Quick quiz
Q1.sp hybridisation produces…
Q2.Bond angles in sp³ hybridisation are…
Q3.How many hybrid orbitals from sp² hybridisation?
Q4.Carbon in C₂H₄ uses which hybridisation?
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Common mistakes
Thinking hybridisation involves electrons, not orbitals. — Correct: Hybridisation mixes orbitals, not electrons; electrons then occupy the hybrids.
Confusing the number of hybrid orbitals with bond angles. — Correct: Number of hybrids = type (sp=2, sp²=3, sp³=4); bond angles follow from geometry (linear 180°, planar 120°, tetrahedral 109.5°).
Ignoring lone pairs when predicting geometry. — Correct: Lone pairs occupy hybrid orbitals and repel bonding pairs, changing observed bond angles (e.g., NH₃ is 107°, not 109.5°).
Assuming all hybrids are filled with electrons. — Correct: Hybrids can hold bonds or lone pairs; the molecule type determines occupancy.
FAQ
Why do atoms undergo hybridisation?
Hybridisation allows atoms to form bonds in directions that maximise overlap and stability, which pure s and p orbitals alone cannot achieve.
Is hybridisation a real physical process?
Hybridisation is a conceptual model to explain bonding geometry. It accurately predicts angles and bond strengths, though it's not a dynamic reorganisation.
How do you determine the hybridisation of an atom?
Count the number of electron groups (bonding + lone pairs) around the atom: 2 = sp, 3 = sp², 4 = sp³.
Can elements use sp³d or sp³d² hybridisation?
Yes — heavy elements (P, S, Cl) can expand their octets and use d orbitals: sp³d (trigonal-bipyramidal), sp³d² (octahedral).