Double and Triple Bonds
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So far, all the the orbital overlaps we encountered were sigma bonds.
Another way that p orbitals can overlap is overlapping both two lobes of each orbital.
This is done by having them parallel to each other.
Here is an illustration of how its done:
This bond is called a pi (
) bond and it occurs in molecules with double or triple bonds.
Since p orbitals extend out along the x-, y-, and z-axes, the x-axis could be a sigma bond (extending out toward another lobe of another atoms orbital) while the other two can form double or triple bonds (by forming one or two pi bonds with other atom's p orbitals).
Basically, here is a compilation of all the things we have discussed:
- The basic molecular framework of a molecule is determined by the arrangement of its sigma bonds.
- Hybrid orbitals are used by an atom to form its sigma bonds and to hold lone pairs of electrons.
- The number of hybrid orbitals needed by an atom in a structure equals the number of atoms to which it is bonded plus the number of lone pairs of electrons in its valence shell.
- When there is a double bond in a molecule, it consists of one sigma bond and one pi bond.
- When there is a triple bond in a molecule, it consists of one sigma bond and two pi bonds.
