p-p pi bonding is stronger than p-d pi bonding,there are basically 2 reasons.1.It is mainly due to the lower energy gap between 2 elements forming p-p pi bonding,say C=O,here both are using 2p orbitals for pi bonding,so obviously the interacting orbitals are very close in energy.For p-d pi bonding the overlap occurs between one p orbital and another d orbital,say for the compound called silicone,stabilised via p-d backbonding,here p-d pi bonding occurs from 2p of Oxygen,to 3d of Silicon.You can easily note that the energy gap between two 2p orbitals is much less than a 2p and a 3d orbital.Better the energy matching better is the overlap and hence the higher strength of bonding.2.Overlap between two orbitals decreases if the distance between the 2nuclei increases.That is why,bond strength of B-B is higher than Ga-Ga.Now,when p-d pi bonding occurs,the distance between the nuclei is generally high,like in case of silicone.distance between Carbon and oxygen nuclei in C=O,is much lower than that between Oxygen and Silicon.That is why,p-d pi bonding is weaker due to higher distance between the nuclei leading to poorer overlap.

Comparison between 3p pi - 3p pi and 3p pi - 3d pi for strength



When comparing the strength between 3p pi - 3p pi and 3p pi - 3d pi, it is important to consider the electronic configurations and bonding characteristics of the involved orbitals. This analysis will help determine which bond is stronger.



The 3p orbitals belong to the third energy level and have a total of three subshells: 3px, 3py, and 3pz. These orbitals are involved in pi bonding, which occurs through the sideways overlap of p orbitals. The 3p pi - 3p pi bond refers to the interaction between two 3p orbitals in a pi bond.



On the other hand, the 3d orbitals belong to the third energy level as well, but they have a different shape and are involved in different types of bonding. The 3p pi - 3d pi bond refers to the interaction between a 3p orbital and a 3d orbital in a pi bond.



To determine which bond is stronger, several factors need to be considered:

1. Energy difference: The energy gap between the two interacting orbitals plays a crucial role in determining bond strength. The energy difference between 3p and 3d orbitals is significant, with 3d orbitals being higher in energy compared to 3p orbitals. This energy gap affects the strength of the bond.

2. Overlap: The extent of overlap between the orbitals also influences bond strength. In the case of 3p pi - 3p pi bond, the overlap occurs between two similar orbitals, resulting in better alignment and stronger bonding. However, in the case of 3p pi - 3d pi bond, the overlap occurs between different orbitals with different shapes, leading to weaker bonding.

3. Electron density: The electron density in the bonding region determines the strength of the bond. In the case of 3p pi - 3p pi bond, the electron density is concentrated between the two 3p orbitals, resulting in a stronger bond. However, in the case of 3p pi - 3d pi bond, the electron density is distributed over a larger region due to the mismatched overlap, resulting in a weaker bond.



Based on the above factors, it can be concluded that the 3p pi - 3p pi bond is generally stronger than the 3p pi - 3d pi bond. The energy similarity, better alignment, and concentrated electron density in the 3p pi - 3p pi bond contribute to its overall strength. However, it is important to note that the strength of a bond can also be influenced by other factors such as electronegativity and molecular geometry.