Group VII Elements - Halogens The Group VII elements are called HALOGENS. The name Halogen means
"salt - former" and is based on the fact that the elements combine
with most metals to form salts. (halides)
ELEMENT
=======
FLUORINE
========
CHLORINE
BROMINE
=======
IODINE
======
State at 20oC
GAS
---
GAS
---
LIQUID
------
SOLID
-----
Colour
PALE YELLOW
PALE GREEN
RED-BROWN
BLACK
Melting Point
(0C)
- 220
- 101
- 7
113
Boiling Point
(0C)
- 188
- 35
59
183
ELECTRON AFFINITY
Electron affinity is the enthalpy change when gaseous atoms of an
element gain electrons to become negative ions.
The FIRST ELECTRON AFFINITY of an element is the ENTHALPY CHANGE WHEN
ONE MOLE OF GASEOUS ATOMS GAINS ELECTRONS TO FORM ONE MOLE OF GASEOUS
IONS.
Electron affinity DECREASES as you DESCEND the group VII:
F à 333kJ
Cl à 346kJ of energy is released for every one mole of F/Cl/Br/I
Br à 324kJ atoms changing to a mole of F/Cl/Br/I ions.
I à 295kJ
This trend can be explained by the fact that as you descend the group,
the X- ion becomes less stable and is therefore less likely to form. H
is less stable because electrons are less strongly attracted due to
the fact that the valence electrons are further from the attractive
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