Stability of PCl5 vs PH5

Electronic Structure
- PCl5 has a stable electronic structure due to the presence of 5 valence electrons in phosphorus, which allows it to form 5 covalent bonds with chlorine atoms.
- PH5, on the other hand, has a less stable electronic structure as phosphorus prefers to form 3 covalent bonds due to its smaller size and higher electronegativity compared to chlorine.

Size and Electronegativity
- Phosphorus is larger in size compared to hydrogen, which makes it difficult for PH5 to achieve a stable structure with 5 hydrogen atoms.
- Additionally, phosphorus has a higher electronegativity than hydrogen, leading to repulsion between the hydrogen atoms in PH5.

Hybridization and Geometry
- In PCl5, phosphorus undergoes sp3d hybridization to accommodate the 5 chlorine atoms, resulting in a trigonal bipyramidal geometry which is more stable.
- In contrast, PH5 would require sp3d2 hybridization to accommodate 5 hydrogen atoms, leading to an unstable structure with distorted geometry.

Intermolecular Forces
- PCl5 exhibits stronger London dispersion forces and dipole-dipole interactions due to the presence of polar P-Cl bonds, contributing to its stability.
- On the other hand, PH5 would have weaker intermolecular forces as hydrogen atoms are less polarizable compared to chlorine atoms, making it less stable.
In conclusion, PCl5 is more stable than PH5 due to its favorable electronic structure, size, electronegativity, hybridization, geometry, and intermolecular forces. These factors contribute to the overall stability of PCl5 compared to the less stable PH5.