Strength of Bonds by 2s-2s, 2p-2p, and 2p-2s Overlap

The strength of chemical bonds is determined by the overlap of atomic orbitals. In the case of 2s-2s, 2p-2p, and 2p-2s overlaps, the strength can be compared by analyzing the characteristics of these orbital interactions.

1. 2s-2s Overlap
When two 2s orbitals overlap, they form a sigma bond. The 2s orbital is spherical in shape and has a higher electron density closer to the nucleus. The overlap between two 2s orbitals is head-on, resulting in efficient sharing of electrons.

2. 2p-2p Overlap
The 2p orbitals are dumbbell-shaped and oriented along three mutually perpendicular axes (x, y, and z). When two 2p orbitals overlap, they can form sigma and pi bonds. The sigma bond is formed by head-on overlap, similar to the 2s-2s overlap. The pi bond is formed by the sideways overlap of two parallel 2p orbitals, which leads to the formation of a double bond or a triple bond.

3. 2p-2s Overlap
The 2p-2s overlap occurs when a 2p orbital from one atom overlaps with a 2s orbital from another atom. This interaction can result in the formation of sigma bonds. However, the strength of the bond formed by 2p-2s overlap is weaker compared to the bonds formed by 2s-2s and 2p-2p overlaps.

Order of Strength
Based on the above information, we can determine the order of strength for the bonds formed by 2s-2s, 2p-2p, and 2p-2s overlaps:

(a) s-s > p-p > p-s
The sigma bond formed by 2s-2s overlap is stronger than the sigma bond formed by 2p-2p overlap. Additionally, the bond formed by 2p-2s overlap is weaker than both the 2s-2s and 2p-2p overlaps. Therefore, the correct order is s-s > p-p > p-s.

In summary, the strength of bonds formed by 2s-2s, 2p-2p, and 2p-2s overlaps follows the order s-s > p-p > p-s. This order is based on the efficiency of electron sharing and the orientation of atomic orbitals involved in the overlap.

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