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Group 7
The Halogens
· They are:
­ Diatomic
­ Form coloured gases
­ Halogen means `salt former'…read more

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Atomic radius and boiling
· The atoms get bigger as you go down the group
because the atomic no. increases so each element has
1 extra filled main level of electrons compared with
the 1 above it.
· Due to the fact the F atoms are so small, there is
repulsion between non bonding e¯ s. Therefore F-F is
weaker than expected. This leads to greater VDW
forces between molecules, increasing the energy
needed to separate the molecules and therefore have
higher melting and boiling points.…read more

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Trends in
Electronegativity is a measure of the
ability of an atom to attract an e¯.
Electronegativity of the halogens
decreases down the group due to an
increase in atomic radius.
Electronegativity depends on nuclear
charge and shielding .
Increased nuclear charge has no
significant effect because there are or
electron shells and more shielding. So
the shared e¯s are further from the
nucleus with an increase in shielding
from more inner shells.
Therefore I atoms attract e¯ in a
covalent bond less strongly than F
atoms.…read more

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Chemical reactions of the
· Displacement reaction- A
more reactive element
displaced(pushes out) the less
reactive element from its
compound.…read more

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How do halogens usually
· By gaining e¯s to become ­ve ions
Cl+ 2e¯ 2Cl¯
· Halogens are good oxidising
agents, so they are reduced.
· An oxidising agent is an agent
that removes e¯s from another

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