The valency of phosphorus in PCl₅ is 5.
Understanding Valency in PCl₅:
Phosphorus forms five bonds with five chlorine atoms, exhibiting a valency of 5.
Electronic Explanation:
- Phosphorus atomic number: 15
- Ground state configuration: [Ne] 3s² 3p³
- In excited state: one 3s electron promotes to 3d orbital
- Excited state: 3s¹ 3p³ 3d¹
- Five unpaired electrons available for bonding
- Each Cl contributes one electron → five P-Cl bonds
Oxidation State vs. Valency:
- Oxidation state of P in PCl₅: +5
- Valency (bonding capacity): 5
- These coincide in this molecule
Key Takeaways:
- Phosphorus shows variable valency (3 in PCl₃, 5 in PCl₅)
- Valency = 5 due to five covalent bonds
- Involves d-orbital participation (expanded octet)