Question

please help with this ? Compare and contrast the compounds NH3 and PH3 in terms of bonding, molecular geometry (shape), and intermolecular forces. Which substance would experience a stronger attraction between its molecules, and why?

Answer 1

 Both compounds are composed of covalent bonds and gaseous under room temperature and pressure. According to data, PH3 has a low boiling point than NH3, though the former being heavier than the later. This is due to intermolecular H- bonding in the later which is absent in the former. The oxidation state of phosphorous in PH3 is (- 3) as that for nitrogen in NH3. Both phosphine and ammonia react with oxygen to produce P2O5 gas and water, and N2 gas and water.

Answer 2

Explanation: Both of these molecules are covalently bonded and are polar in nature. Since they are polar covalent molecules, they have dipole-dipole inter molecular forces of attraction.

In ammonia, N atom is the central atom and three H atoms are bonded to it and N atom has one lone pair of electrons due to which its molecular geometry is trigonal pyramidal.  Similarly, in phosphine, P is the central atom and three H atoms are bonded to it and it has one lone pair of electrons due to which its molecular geometry is trigonal pyramidal.

Nitrogen is more electron negative than phosphorous. Hydrogen boding is present in ammonia as hydrogen atoms are bonded to more electron negative nitrogen atom.

Due to the presence of hydrogen bonding, ammonia molecule experience stronger attraction forces as compared to phosphine.