6.2 Group 7
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What is group 7 known as
The Halogens
Name the halogens
-Flourine -Chlorine -Bromine -Iodine -Astatine
Why do group 7 elements have similar properties
They all have 7 electrons in their outer shell
How do the melting and boiling points of halogens change down the group
They increase down the group
Chlorine at room temperature
A green gas
Bromine at room temperature
A red-brown liquid which gives off orange vapour
Iodine at room temperature
A dark grey crystalline solid which gives off purple vapour when heated
Test for chlorine
-Hold a piece of damp blue litmus paper over it -Chlorine will turn red then bleach the paper white
Why does the damp blue litmus paper first turn red when in contact with chlorine
A solution of chlorine is acidic
How does reactivity in group 7 change
It decreases down the group
Why does reactivity of group 7 elements decrease down the group
It becomes harder to attract the extra electron as the outer shell is further away from the nucleus so there is weaker forces as the atomic radius is larger
Why are halogens very reactive
They only need to gain one electron to gain a stable electronic structure
Halogen + metal reaction
Metal + halogen -> halide salt
Halogen + hydrogen reaction
Hydrogen + halogen -> hydrogen halide
What happens when a hydrogen halide dissolves in water
It forms an acid
What happens when a more reactive halogen reacts with a halogen compound
A displacement reaction occurs, so the less reactive halogen is displaced and replaced by the more reactive halogen
How to show the reactivity trend of halogens
Using displacement reactions
Experiment to investigate the reactivity of halogens
-Measure out a small amount of a halide salt solution in a test tube -Add a few drops of a halogen solution to it and shake gently -If you see a colour change the halogen solution was more reactive
Explain what a colour change when adding a halogen solution to a halide salt solution means
The halogen solution was more reactive and displaced the halide ion from the compound
Chlorine water colour
Colourless
Bromine water colour
Orange
Iodine water colour
Brown
Chloride salt solution + chlorine water
No reaction
Chloride salt solution + bromine water
No reaction