Class 11 Chapter 3 Hybridization
Introduction
Hybridization is the concept of mixing atomic orbitals of similar energies on an atom to form new hybrid orbitals, which explain observed molecular shapes and bond angles better than pure atomic orbitals.
Concept of Hybridization
When atomic orbitals combine to form hybrid orbitals, the number and type of hybrids depend on the number of atomic orbitals mixed. Each hybrid orbital has a specific shape and orientation, accommodating bonding electron pairs.
Types of Hybridization
sp Hybridization
Mixing one s and one p orbital yields two sp hybrids, arranged linearly (180°). Examples: BeCl2, acetylene (C₂H₂).
sp² Hybridization
One s and two p orbitals mix to form three sp² hybrids, arranged trigonal planar (120°). Examples: BF3, ethylene (C₂H₄).
sp³ Hybridization
One s and three p orbitals combine to form four sp³ hybrids, oriented tetrahedrally (109.5°). Examples: CH4, NH4+.
dsp² & sp³d Hybridization
Involving d orbitals, dsp² (one d + one s + two p) yields square planar geometry (e.g., [Ni(CN)4]2–), while sp³d (one s + three p + one d) yields trigonal bipyramidal shape (e.g., PCl5).
Orbital Diagrams & Examples
Orbital energy-level diagrams illustrate which atomic orbitals mix. For each hybridization type, the new orbitals are equal in energy and directed according to the molecular geometry:
| Hybridization | Geometry | Example Molecule |
|---|---|---|
| sp | Linear (180°) | BeCl2, C₂H₂ |
| sp² | Trigonal planar (120°) | BF3, C₂H₄ |
| sp³ | Tetrahedral (109.5°) | CH4, NH3 |
| dsp² | Square planar (90°) | [Ni(CN)4]2– |
| sp³d | Trigonal bipyramidal (90°,120°) | PCl5 |
Factors Affecting Hybridization
- Energy compatibility of orbitals
- Electronegativity of central atom
- Presence of multiple bonds (π-bonds use unhybridized p orbitals)
- Coordination number and steric requirements
Significance in Molecular Geometry
Hybridization explains observed bond angles and molecular shapes, providing a straightforward way to predict geometry, polarity, and reactivity of molecules in organic and inorganic chemistry.
Conclusion
Understanding hybridization is essential for rationalizing molecular structures and bonding. It bridges the gap between simple Lewis formulas and three-dimensional shapes observed experimentally.
