0:00 / 0:00
Sigma (σ) and Pi (π) Bonds
There are two ways orbitals can overlap:
- Sigma (σ) type overlap, and pi (π) type overlap.
- Sigma overlap is when 2 electrons in a bond are localized between 2 nuclei (along the internuclear axis)
- Formed from the end-to-end overlap of hybridized orbitals (or orbitals s orbital for H)
- Pi overlap is when 2 electrons are localized in the region above and below the plane formed by 2 bonded nuclei (occurs above and below the internuclear axis)
- Formed from side to side alignment of unhybridized p orbitals in adjacent atoms to form a bond
Figure 14.2 Sigma and Pi type Overlap.
If asked how many sigma and pi bonds there are in a molecule, it's very simple to count!
Wize Tip
For every single bond you see = 1 sigma bond
For every double bond you see= 1 sigma bond AND 1 pi bond
For every triple bond you see= 1 sigma bond AND 2 pi bonds
Ex. In this molecule of aspartic acid, how many sigma and pi bonds are there?
a) Sigma bonds:
15
b) Pi bonds:
2
Propyne, H3CCCH, has how many sigma () and pi () bonds, respectively?