GROUP 7: HALOGENS

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PHYSICAL PROPERTIES OF HALOGENS

at room temp:- 

Flourine and chlorine= GASES

Bromine= LIQUID 

Iodine = SOLID

Halogens are all coloured elements and are all TOXIC and CORROSIVE

(http://www.clker.com/cliparts/c/2/a/b/11954220161423934091h0us3s_Sign_danger_toxic.svg)(http://www.clker.com/cliparts/7/4/6/2/11954219911140919487h0us3s_Sign_danger_corrosive.svg)


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HALOGEN REACTIONS

- Halogens all have similar reactions because they're in the same group. 

- All react with metals to form metal halides.

eg:

POTASSIUM + BROMINE >>>> POTASSIUM BROMIDE

     2K (s)       + Br2 (l)      >>>>> 2KBr (s)

CALCIUM + CHLORINE >>>> CALCIUM CHLORIDE

    Ca (s)    + Cl2 (g)       >>>>> CaCl2 (s)

Each halogen need ONE more electron to complete its outer shell, so they all form ions with a charge of -1. Flourine is the most reactive halogen and iodine is the least reactive. 

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MORE HALOGEN REACTIONS

Halogens and hydrogen

halogens react with hydrogen to form hydrogen halides.

These form acids when dissolved in water. 

eg: flourine + water = hydrogen flouride. 

Displacement reactions 

-Bromine can be displaced from a solution of bromide salts by reacting them with CHLORINE.

sodium bromide + chlorine = sodium chloride + bromine 

2NaBr (aq) + Cl2 (g) =2NaCl + Br2

Chlorine will also displace iodide ions and the solution will turn brown-black as iodine is formed.

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REACTIVITY OF THE HALOGENS

If you add chlorine to a compound of fluorine, there will be no reaction.

Why? 

Reactivity

Displacement reactions (see previous card) can be used to work out how reactive the different halogens are. 

a more reactive halogen will displace a less reactive one.

Chlorine is more reactive than iodine so it displaces iodine.

Chlorine is also more reactive than bromine, so it displaces bromine from bromide.


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