Group 7 - Halogens

• These are non-metals
• They exsit as diatomic molecules (as two molecules).

F2

Cl2

Br2

I2

• There are 7 electrons in their outershell.
• Halogens react by gaining 1 electron to make a full outershell (opposite to Group 1 - Alkali metals in every aspect).

Cl + 1 electron → Cl-

• Going down the group the outershell is further away from the nucleus.
• This is why reactivity decreases going down the group.

• Reactivity can be seen by a displacement reaction between the halogens & the halide ions.

Halogens:

Chloride water - Cl2(aq) → colourless most reactive

Bromine water - Br2(aq) → orange

Iodine solution - I2(aq) → brown least reactive

Halides (all colourless):

Sodium chloride solution - NaCl → Cl-(aq) most reactive

Sodium bromide solution - NaBr → Br-(aq)

Sodium iodide solution - NaI → I-(aq) least reactive

• A more reactive halogen will displace a less…