1. Halogens
L.O: To be able to explain the properties and patterns of reactivity of the halogens
Starter:
Choose a halogen and draw the electronic structure of it.
What do the halogens do when they react?
Challenge: can you write a half equation to show this?

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. Are there any differences between these reactions? Why?
Aluminium and chlorine NE
Aluminium and bromine
WVXM

4. Can you hypothesis why there are these differences

5. Displacement reactions State Symbols
These symbols are used in some equations:
(aq) aqueous solution
(l) Liquid
(s) Solid
(g) Gas
e.g. 2K(s) + 2H2O (l) → 2KOH(aq) + H2(g)

6. practical

7. Patterns: reactivity F2 Cl2 Br2 I2
Reactivity increases up the group.
For example, their reaction with hydrogen F2
Reacts instantly even at
-200ºC
Cl2
Reacts slowly in dark.Explodes in light
Br2
Needs heating to +200ºC in order to react I2
Does not react completely even at 500ºC 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. 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?

10. Patterns: physical state
What patterns does this data show?
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

11. 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

12. Have Coloured Vapours (getting darker down the group)
The Halogens
Have Coloured Vapours (getting darker down the group) F Cl
Form -1 ions by GAINING one electron Br
Form covalent bonds with each other to form DIATOMIC Molecules I
A more reactive halogen can DISPLACE a less reactive halogen from an aqueous solution At
As you go DOWN the group
Halogens get Less REACTIVE as you go DOWN the group (larger atoms gain electrons less easily)
The shells provide SHEILDING from the positive pull of the nucleus so it becomes HARDER to pull in an electron
The HIGHER the MELTING / BOILING point

13. The Halogens - Summary F Cl Br I At
Halogens get _______ REACTIVE as you go DOWN the group.
The shells provide __________from the positive pull of the nucleus so it becomes HARDER to pull in an electron
A more reactive halogen can ________ a less reactive halogen from an aqueous solution
The coloured vapours get getting ________ down the group Cl Br I At

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