1. The Physical and Chemical Properties of the Group 7 elements
Fluorine Atomic Number 9 Mass Number 19
Chlorine Atomic Number 17 Mass Number 35
Bromine Atomic Number 35 Mass Number 80
Iodine Atomic Number 53 Mass Number 127
What is the number of protons, electrons and neutrons for each element?
What is the electronic configuration for the first two elements?
Why are the elements all in group 7?

2. ANSWERS Element Fluorine 9 10 2,7 Chlorine 17 18 2,8,7 Bromine 35 45
protons
neutrons
electrons
arrangement
Fluorine 9 10
2,7
Chlorine 17 18
2,8,7
Bromine 35 45
2,8,18,7
Iodine 53 74
2,8,18,8,7
ALL HAVE 7 electrons in outer shell

3. Physical Properties Structure Melting/boiling Points Colour
See the video on Firefly ‘Group 7 elements’

4. Structure All are diatomic molecules F2, Cl2, Br2, I2
There is a COVALENT BOND between the atoms in the molecule

5. Melting/boiling points
Fluorine oC -188oC
Chlorine oC -34oC
Bromine -7oC +58oC
Iodine oC +184oC
State at RT
Trend in mp/bp

6. ANSWERS All have Low melting/boiling points.
All are Simple molecular structures
Melting/boiling points increases down group.
Iodine sublimes on heating. (Turns from solid Gas)

7. Chemical Properties REACTIVITY
Reaction with other halides (displacements)

8. REACTIVITY I
Download the video from Firefly ‘Group 7 for sep’
Observe and note trend in reactivity

9. REACTIVITY II Reactivity decreases down the group as illustrated by
Reactions with metals get less violent and slower

10. REACTIVITY III NB Full outer shell = stable atom
NB In reactions atoms lose/gain or share electrons to achieve full outer shell
NB Group 7 elements have 7 electron in their outer shell
SO to achieve full outer shell they:
GAIN ONE ELECTRON during reactions.
SHARE ONE ELECTRON during reactions

12. REACTIVITY IV
Further the electron in outer shell is from the nucleus the harder it is to gain/share.
Closer the electron in outer shell is to the nucleus the easier it is to gain/share.
Inner shells SHIELD (dilute) effect of nucleus.

13. Displacement reactions of Halogens
IDEA
Will a more reactive halogen displace a less reactive halogen?
How could we test this idea?
What problems might there be (considering the elemental state of these elements)?
All of the halogens dissolve in petrol.
Sodium Chloride, Sodium Bromide and Sodium Iodide are readily available

14. A more reactive halogen will displace a less reactive halogen from its compound
Practical Add a small amount of a halogen to a test tube
Add a few drops of hexane
Add a small amount of solution containing a Potassium halide.
Observe the colour of the petrol at the end of the reaction.

15. Results Halogen at start Colour of petrol layer at start
Potassium halide
Colour of petrol layer at the end
Halogen at end
Has a displacement taken place
Chlorine
Pale Green
Potassium Bromide
Orange
Bromine
Yes,
Chlorine has removed Bromine from its compound
Potassium Iodide
Purple
Iodine
Chlorine has removed Iodine from its compound
Potassium Chloride No
Bromine has not removed chlorine from its compound
Bromine has removed Iodine from its compound
Iodine has not removed chlorine from its compound
Iodine has not removed Bromine from its compound

16. Cl2 + 2KI  2KCl + I2 (if we remove K+ from both sides we get)
Cl2 + 2I- 2Cl- + I2
HENCE
Cl2  2Cl-
2I-  I2
The more reactive halogen is GAINING electrons going from neutral to negative. It is being REDUCED
The general equation would be
X2 + 2Y-  2X- + Y2 (where Y is below X in Group)