Introduction:
Ammonia (NH3) and phosphine (PH3) are both hydride compounds of nonmetals. While ammonia readily dissolves in water, phosphine does not exhibit the same behavior. This difference in solubility can be explained by examining their structural and chemical properties.

Structural Differences:
- Ammonia (NH3) is a polar molecule due to the presence of a lone pair of electrons on the nitrogen atom. The electronegativity difference between nitrogen and hydrogen leads to a partial positive charge on the hydrogen atoms and a partial negative charge on the nitrogen atom. This polarity gives ammonia the ability to form hydrogen bonds with water molecules.
- Phosphine (PH3), on the other hand, is a nonpolar molecule. The phosphorus atom is less electronegative than hydrogen, resulting in a lack of significant polarity. As a nonpolar molecule, phosphine cannot form hydrogen bonds with water.

Hydrogen Bonding:
- Water molecules are highly polar due to the electronegativity difference between oxygen and hydrogen. The oxygen atom carries a partial negative charge, while the hydrogen atoms have partial positive charges. This polarity allows water molecules to form hydrogen bonds with other polar molecules or ions.
- In the case of ammonia, the lone pair of electrons on the nitrogen atom can form hydrogen bonds with the partially positive hydrogen atoms of water molecules. This interaction between ammonia and water enables the dissolution of ammonia in water.
- Phosphine lacks the necessary polarity to form hydrogen bonds with water molecules. As a result, the intermolecular forces between phosphine and water are weak, preventing significant dissolution of phosphine in water.

Hydration Energy:
- The dissolution of a solute in a solvent is an energetically favorable process if the energy released from the formation of new solute-solvent interactions (hydration energy) is greater than the energy required to break the solute-solute and solvent-solvent interactions.
- In the case of ammonia, the hydration energy gained from the formation of hydrogen bonds with water molecules is greater than the energy required to break the ammonia-ammonia and water-water interactions. Therefore, ammonia is soluble in water.
- Phosphine, lacking the ability to form strong hydrogen bonds with water, has a lower hydration energy compared to ammonia. The energy required to break the existing solute-solute and solvent-solvent interactions is greater than the hydration energy gained. Consequently, phosphine does not dissolve significantly in water.

Conclusion:
In summary, the solubility of ammonia in water can be attributed to its polarity and ability to form hydrogen bonds, while phosphine's lack of polarity and inability to form hydrogen bonds limit its solubility in water. These structural and chemical differences between NH3 and PH3 result in contrasting solubility behaviors.

Because non polar ph bond but water is Polar in mature