Example 1 · level 1
What is the hybridisation of the C atom in CO₂?
- sp³d
- sp²
- sp
- sp³
Show solution
- In CO₂: 2 σ bonds (two C=O), 0 lone pairs → steric number 2; linear.
- Steric number 2 → sp.
Answer: sp
CLASS 11–12 CHEMISTRY · CHEMICAL BONDING AND MOLECULAR STRUCTURE
Hybridisation of a central atom
Steric number = σ bonds + lone pairs on the atom (a double or triple bond counts as one σ bond). 2 → sp, 3 → sp², 4 → sp³, 5 → sp³d, 6 → sp³d², 7 → sp³d³.
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Worked examples
Example 2 · level 2
What is the hybridisation of the N atom in NH₄⁺?
- sp³d²
- sp²
- sp³d
- sp³
Show solution
- In NH₄⁺: 4 σ bonds, 0 lone pairs → steric number 4; tetrahedral.
- Steric number 4 → sp³.
Answer: sp³
Example 3 · level 3
What is the hybridisation of the P atom in PCl₅?
- sp³d
- sp³
- sp³d²
- sp³d³
Show solution
- In PCl₅: 5 σ bonds, 0 lone pairs → steric number 5; trigonal bipyramidal.
- Steric number 5 → sp³d.
Answer: sp³d