Question

1) Build models for the PH₃ and PH₄⁺ species.

How do you compare the angles of H - P - H bonds in both species? If different, explain why.

How do you compare your electronic and molecular geometries?

2 )Build the models for the PH₃ and H₂S species.

How do you compare the binding angles in both species? If they are different, explain why.

How do you compare your electronic and molecular geometries?

Answer 1

1) PH₃ consist of 3 bond pairs and one lone pair on the central atom P leads to the pyramidal structure. Due to larger repulsion between the lone pair -bond pair (lp-bp) electrons, the bond angle of P-H-P bond decreases from normal tetrahedral geometry of 109.5 degrees. The P-H-P bond angle in PH₃ is 93.6 degrees. While PH₄⁺ species consist of 4 bond pairs which exhibit a tetrahedral geometry. Thus the P_H_P bond angle in PH₄⁺ is 109.5 degrees.

In PH₃, the central atom contains 4 bond pair electrons and the electronic geometry of PH₃ is tetrahedral and molecular geometry of triangular pyramidal geometry. But PH₄⁺ have both tetrahedral electronic and molecular geometries. The molecular geometry considers only the arrangement of the bonds. It ignores the lone pairs. But the electronic geometry consider both arrangement of both bond pairs and lone pairs

2) PH₃ consist of 3 bond pairs and one lone pair on the central atom P leads to the pyramidal structure. Due to larger repulsion between the lone pair -bond pair (lp-bp) electrons, the bond angle of P-H-P bond decreases from normal tetrahedral geometry of 109.5 degrees. The P-H-P bond angle in PH₃ is 93.6 degrees. H₂S consists of 2 bond pairs and 2 lone pairs. the lone pair -lone pair repulsion is stronger than lone pair bone pair repulsion. Hence the bond angle in H₂S will be smaller than PH₃. the bond angle in H₂S is 92.5 degrees.

the electronic geometry of PH₃ is tetrahedral while molecular geometry is pyramidal

the electronic geometry of H₂S is tetrahedral while the molecular geometry is bend shape