Physical properties of
halogens
Electronic configurations
• Halogens are in group VII of the
periodic table and so have seven
electrons in their outer shell.
• F 1s2 2s2 2p5
• Cl 1s2 2s2 2p5 3s2 3p5
• Br 1s2 2s2 2p5 3s2 3p5 4s2 (3d10) 4p5
• I 1s2 2s2 2p5 3s2 3p5 4s2 (3d10) 4p5
5s2 (4d10) 5p5
Bonding
• Halogens require one electron to
complete their outer shell.
• This can be obtained by gaining an
electron to form a halide anion.
• Eg: Cl
+
e
→
Cl
• Alternatively they can share electrons
in a single covalent bond;
• Clx + Hx → ClxxH
Diatomic molecules
• The halogens are found in their native states
as diatomic molecules.
• F:F
• Cl:Cl
• Br:Br
• I:I
• Halogens form simple molecular lattices held
together by weak van der Waals forces.
Chlorine is a pale green gas at
room temp and pressure.
Bromine is an orange brown liquid
at room temp and pressure.
It has a low BP and is highly volatile.
Iodine is a grey, silvery solid at room
temperature and pressure.
Iodine will not melt, on heating it
sublimes, forming a purple gas.
MPs and BPs
F
Cl
Br
I
MP (oC)
-220
-101
-7
113
BP (oC)
-188
-35
59
Plot the MPs and BPs and explain the trend in terms of
structure/bonding.
MPs and BPs of halogens
• The MPs and BPs increase down the
group.
• This is because there are more
electrons in the atoms.
• Which means that the van der Waals
forces between molecules become
stronger.
• So more energy is required to break
them and melt or boil the sample.
Solubility of halogens
Organic layer
non-polar
solvent.
Halogens are
more soluble
in non-polar
than in polar
solvents.
Aqueous
layer polar
solvent
The bond
between
atoms is not
polarised.
Bromine water shaken with hexane.
Solubility of
chlorine
Chlorine is not
very soluble in
water, but reacts
to form pale
green chlorine
water.
Chlorine is more
soluble in organic
solvents.
Aqueous
layer
Solubility of
bromine
Bromine readily
dissolves in
water to give an
orange brown
solution.
Bromine is more
soluble in organic
solvents.
Solubility of
iodine
Iodine is not
very soluble in
water.
But it is much
more soluble in
KI, giving a yellow
brown solution.
Iodine is much
more soluble in
organic
solvents.
Organic layer
Aqueous
layer