In redox reactions an oxidant (oxidizing agent) and a reductant (reducing agent) react by electron transfer.
In general reaction occurs only if the halogen is above the halide in the periodic table.
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The reaction above occurs because
The reverse of the reaction (I2 + 2Br–
Br2 + 2I– ) does not occur.
This is because
The next three review pages have short videos of the reactions of the various halogens with the halides. We hope that you will enjoy seeing some experiments being done. Thanks to Mike Thompson for making these available to us.
The questions start again on page 11. If you click on the Reviews link near the top right of the screen, it will bring up all of the Review Pages on a single page. You may find that useful for connecting the reactions that you see with what has been described above.
Halogens are oxidants (electron acceptors).
Halide ions are reductants (electron donors).
A halogen may react with a halide ion by electron transfer.
The products of the reaction are also a halogen and a halide.
Example: Br2 + 2I– I2 + 2Br–
Which halides and halogens react?Halide ions are reductants (electron donors).
A halogen may react with a halide ion by electron transfer.
The products of the reaction are also a halogen and a halide.
Example: Br2 + 2I–
I2 + 2Br–In general reaction occurs only if the halogen is above the halide in the periodic table.
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The reaction above occurs because
the halogen in the reactants (Br2) is a stronger oxidant (electron acceptor - oxidising agent) than the halogen in the products (I2) AND
the halide in the reactants (I– ) is a stronger reductant (electron donor - reducing agent) than the halide in the products (Br–)
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the halide in the reactants (I– ) is a stronger reductant (electron donor - reducing agent) than the halide in the products (Br–)
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| Oxidant strength | Elemental form | Most common ion | Reductant strength |
very strong moderate | F2 (fluorine) | F– (fluoride) | very weak moderate |
| Cl2 (chlorine) | Cl– (chloride) | ||
| Br2 (bromine) | Br– (bromide) | ||
| I2 (iodine) | I– (iodide) |
The reverse of the reaction (I2 + 2Br–
Br2 + 2I– ) does not occur.This is because
the halogen in the reactants (I2) is a weaker oxidant (electron acceptor) than the halogen in the products (Br2).
Note that the halogen that is more electronegative is a better oxidant (electron acceptor)
The halide ion in the reactants (Br –) is a weaker reductant (electron donor) than the halide ion in the products (I– ).The next three review pages have short videos of the reactions of the various halogens with the halides. We hope that you will enjoy seeing some experiments being done. Thanks to Mike Thompson for making these available to us.
The questions start again on page 11. If you click on the Reviews link near the top right of the screen, it will bring up all of the Review Pages on a single page. You may find that useful for connecting the reactions that you see with what has been described above.