Multiple Bonds (DP IB Chemistry): Revision Note
Multiple bonds
Non-metal atoms can share more than one pair of electrons to form single, double, or triple covalent bonds
Sharing electrons allows both atoms to achieve a noble gas configuration
This increases the stability of the atoms
The type of covalent bond relates directly to the number of shared electrons:
Single bond (C–C) = 2 shared electrons
Double bond (C=C) = 4 shared electrons
Triple bond (C≡C) = 6 shared electrons
Quadruple covalent bonds are not possible
The repulsion between 8 electrons between the two nuclei is too great
Bond energy
Bond energy is the amount of energy required to break one mole of a covalent bond in the gaseous state
Bond energy has units of kJ mol-1
It is a measure of bond strength:
The higher the bond energy, the stronger the bond
Bond length
Bond length is the distance between the nuclei of two covalently bonded atoms
As more electrons are shared, the electron density between the atoms increases
This increases the electrostatic attraction between the bonding electrons and the nuclei
The stronger attraction pulls the atoms closer together
This means that:
Bond length decreases
Bond strength increases
Triple bonds are the shortest and, therefore, the strongest covalent bonds
This is due to the high electron density between the nuclei
Carbon-carbon bond lengths

Examiner Tips and Tricks
Remember:
Single bonds = longest and weakest
Triple bonds = shortest and strongest
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