The Halogens

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Chemistry In Action
11.1- The Halogens
I already know about the group 7 elements.
E.g. Chlorine:
7 electrons in the outermost shell
None metal
Has a very low melting/boiling point
Forms diatomic molecules
Highly electronegative
Does not conduct electricity
Physical Properties
The gaseous halogens vary in appearance. They get darker and denser as
we go down the group.
They all have a characteristic "swimming pool" smell.
When studying groups you look for the trends and know them. You then
note the exceptions in the trend.
E.g. the bond energies between the atoms of the elements decrease as
you go down the group. You can explain this trend by noting the distance
between the shared pair of electrons and the positive nuclei and the
shielding effect.
But there is as exception: FLUORINE
The explanation for this exception is that due to the small size of the
fluorine atoms there is repulsion between the none bonding electrons,
Element Colour
Flourine Yellow
Chlorine Greenish
Bromine Brick Red
Iodine Black Solid
Matthew Thomas
The Maelor School

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Chemistry In Action
Size Of Atoms
The atoms get bigger as we go down the group because each element
has one extra filled main level of electrons compared with the one above.
Atomic Melting Boiling
Atomic Electron
Halogen Electronegativity Radius Point Point
Number, Z Arrangement (T_m/K)
(nm) (T_b/K)
Fluorine 9 [He] 2s2 2p5 4 0.071 53 85
Chlorine 17 [Ne] 3s2 3p5 3 0.099 172 238
[Ar] 3d10 4s2
Bromine 35 2.8 0.114 266 332
[Kr] 4d10 5s2
Iodine 53 2.5 0.…read more

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Chemistry In Action
Remember to write a
halogen element as a
diatomic molecule e.g. F2,
not F.
Increase as we go down the group. This is because the larger atoms have
more electrons and this makes the van der Waals forces between the
molecules stronger. The lower the boiling point the more volatile the
element. So chlorine, which is a gas at room temperature, is more volatile
than iodine, which is solid.…read more


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