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Group 7
The Halogens
The halogens are the elements in group 7 of the periodic table.

All halogen atoms have seven electrons in the outer shell.

The halogens are the most reactive group of non-metals, and none of them is found
naturally in the element form.

They are all found…

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Bonds between Molecules
The intramolecular bonds are covalent.

The intermolecular bonds are instantaneous dipole ­ induced dipole.

As the size of the molecule and number of electrons increases, so does the strength of the
intermolecular bonds.

This explains why the physical state of halogens changes from gas to liquid to…

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Overall, this means that fluorine is the most reactive member of the halogen group, and
reactivity decreases as the group is descended.

Chemical properties of the halogens



Fluorine Chlorine Bromine Iodine
Relative Most reactive More reactive than More reactive Least reactive
reactivity bromine or iodine than iodine,
less reactive
than…

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Halogens as Oxidising Agents
The halogens are the most reactive non-metals in the periodic table and are strong
oxidising agents removing electrons in reactions.

Oxidation is loss of electrons.

The oxidising power of a halogen is a measure of the strength with which a halogen atom is
able to attract…

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Redox Reactions of the Halogens
Redox reactions can show that the halogens become less able to form halide ions down the
group.

You can show the decrease in reactivity using redox reactions of:

Aqueous solutions of halide ions Cl- (aq), Br- (aq) and I- (aq)
Aqueous solutions of halogens Cl2…

Page 6

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Electrolysis of Halide Solutions
When you electrolyse aqueous solutions containing iodide or bromide ions, the halogen
element is released at the anode (the positive electrode).

The halide ions lose electrons to the electrode and are oxidised to atoms, which combine to
form molecules.

For example, electrolysing sodium bromide solution produces…

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Storing and Transporting Halogens
The more reactive halogens can be quite dangerous.

They must be kept away from flammable materials as they are oxidising agents and
increase fire risks.

They are also toxic and corrosive, so must be kept away from skin and eyes.



Fluorine

Fluorine is the most reactive…

Page 8

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Uses of Halogens
Although they are hazardous, the halogens are widely used because they are needed to
make many useful compounds.

Halogen Used to make Useful properties Used for
Fluorine PTFE ­ Inert, low friction, Non-stick coating on
polytetrafluroethene thermally stable pans

HCFCs Inert, gas at room Refrigerant
temperature

Sodium…

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