1. THE HALOGENS

2. Halogens and the Periodic Table
These are the Halogens or Group 7 Elements H Li Na K Rb Cs Fr Be Sc Ti Mg V Cr Mn Fe Co Ni Cu Zn Ga Ge Se Br Ca Kr Y Zr Nb Mo Tc Ru Pd Ag Cd In Sn Sb Sr Te Rh Ba Hf Ta W Re Os Ir Au Hg Tl Pb Bi Po La At Pt Ra Rf Db Sg Bh Hs Mt ? Ac Al P N O S Cl F Ne Ar Rn I Si Xe He B C As Br At Cl F I

3. Electronic Structure
All the Group 7 elements have 7 electrons in the outermost shell.
Fluorine
2,7 F Cl Br I At
Chlorine
2,8,7
Bromine
Iodine
Astatine
And so on

4. Halogen molecules
All the Group 7 elements are molecules containing two atoms. (They are diatomic)
Each atom is 1 electron short of a noble gas electron structure.
By sharing electrons in a covalent bond full outer electron shells are achieved. F F

5. What colour would you expect astatine to be?
Patterns: colour
The group 7 elements get darker as you go down the group.
Bromine solution.
Note the bromine vapour above the liquid F Cl Br I
Darker a
What colour would you expect astatine to be?

6. Patterns: physical state
Melting Points and boiling points increase as the molecules get bigger.
What is the physical state: solid, liquid or gas?
Element
Size
Melting Point (oC)
Boiling Point (oC)
Physical State
Fluorine
-220
-188
Chlorine
-101
-35
Bromine -7 59
Iodine
+114
184
gas
gas
liquid
solid

7. Patterns: reactivity F2 Cl2 Br2 I2
Reactivity increases up the group.
For example, their reaction with hydrogen F2
Reacts instantly even at C
Cl2
Reacts slowly in dark.Explodes in light
Br2
Needs heating to +200 C in order to react I2
Does not react completely even at 500 C F Cl Br I At
Increasing Reactivity
How will Astatine react?

8. Reactivity and electron structures
Most halogen reactions involve gaining an electron.
The atoms get bigger as you go down the group. This reduces the attraction of the (+) nucleus for an additional (-) electron.
‘Shielding’ by the inner electron shells also reduces the attraction from the nucleus.
As we go down the group the tendency to gain electrons decreases and so does the reactivity
Reactivity decreases

9. Displacement reactions
A more reactive halogen will displace a less reactive halide from its compounds in solution.
Chlorine + sodium bromide 
sodium chloride + bromine
Cl2(aq) + 2NaBr(aq)  2
NaCl(aq) + Br2(aq)
very pale green no
colour
red colour no
colour

10. Displacement theory Cl
Na+ F-
Cl- F e-
The attraction of halogens for an extra electron gets greater going up the group:
I <Br<Cl<F.
If we mix a metal halide with a more reactive halogen, the electron will be transferred from the less to the more reactive halogen.

11. fluorine-containing polymers, e.g. Teflon
Uses of Fluorine
Fluorine, often via hydrogen fluoride, is used to manufacture many other products.
Toothpaste,
to prevent tooth decay
Fluorine
and its
compounds
Processing uranium
nuclear fuel
fluorine-containing polymers, e.g. Teflon
Fluoridation of water

12. Uses of Chlorine antiseptics and disinfectants pesticides
and weed killer
Chlorine
and its compounds
HCl
Bleach to kill bacteria
and to make paper
white
Drinking water treatment
Chlorinated
carbon compounds, e.g.
solvents and plastics (PVC)

13. Uses of Bromine and Iodine
and its
compounds
Leaded petrol
(being phased out)
medicines
photography
agriculture
Iodine and its compounds
antiseptic
Animal feed supplements

14. Uses of Halogens
Link up the halogen with the uses. Br Cl F I

15. How many electrons do the halogens have in their outer shell?1 5 7 8

16. How many atoms exist in a halogen molecule?1 2 5 7

17. What is the order of increasing reactivity of the halogens?
F, Cl, I, Br
F, Cl, Br, I
I, Cl, Br, F
I, Br, Cl, F

18. Which of the pairs of reactants will NOT result in a displacement reaction?
Iodine + sodium chloride
Fluorine + sodium chloride
Chlorine + sodium iodide
Bromine + sodium iodide

19. What halogen is used in non-stick cooking pans?F Cl Br I

20. What halogen is used in animal feed?Cl Br I

21. Astatine comes below iodine in Group 7 What might its melting point be (in oC)?
A. – B C D. +300

22. 1 2 3 4 5 6 7 8 9 Across: 2 Reactivity does this going up group 7
5 Added to animal feeds
7 Number of outer shell electrons in halogens
8 Used in the swimming pool
9 Used in photography
Down:
1 Name for Group 7 Elements
3 Most reactive halogen
4 Type of compounds formed with non-metals
6 Type of compounds formed with metals 1 2 3 4 5 6 7 8 9