Pi bond facts for kids
A pi bond (also written as π bond) is a special type of chemical bond. It happens when two atoms share electrons in a unique way. Imagine the path of an electron as a figure-eight shape, like a dumbbell. In a pi bond, these electron paths from two different atoms cross over each other.
The Greek letter π (pi) in the name comes from p orbitals. These are the specific electron paths that usually form pi bonds. When you look along the line connecting the two atoms, the pi bond looks similar to a p orbital.
Pi bonds are usually not as strong as another type of bond called a sigma bond. This is because the electron paths in a pi bond are parallel to each other. This means they don't overlap as much as in a sigma bond, making the connection a bit weaker.
When atoms form a pi bond, their electron paths overlap in two areas. The electrons involved in these bonds are sometimes called pi electrons. Once a pi bond is formed, the parts of the molecule connected by it cannot easily spin around that bond. If they tried to spin, the pi bond would break because the parallel electron paths would no longer line up.
Multiple Bonds
When atoms are joined by a double bond, it means they have one sigma bond and one pi bond between them. If they are joined by a triple bond, they have one sigma bond and two pi bonds.
Even though a single pi bond is weaker than a sigma bond, having both a sigma and a pi bond together makes the overall connection much stronger than just a single sigma bond. This extra strength is why multiple bonds are shorter than single bonds.
For example, let's look at carbon-carbon bonds:
- In ethane, which has only single bonds, the carbon-carbon bond is 154 pm long.
- In ethylene, which has a double bond, the carbon-carbon bond is shorter at 134 pm.
- In acetylene, which has a triple bond, the carbon-carbon bond is even shorter at 120 pm.
This shows that more bonds between atoms lead to shorter and stronger connections.
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| ethane | ethylene | acetylene |
Images for kids
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Ethylene (ethene), a small organic molecule containing a pi bond, shown in green.
See also
In Spanish: Enlace π para niños
