The halogens

How do the halogens occur as on Earth

They occur as stable halide ions in sea water or combined with sodium or potassium

What do the halogens exist as at RTP

They exist as diatomic molecules X₂

What is the trend in boiling points going down the group

It increases as there are more electrons so stronger London forces which means more energy is required to break them

What happens to the halogens in redox reactions

Each halogen atom is reduced, gaining one electron to form a 1- halide ion, they are oxidising agents

What is the trend in displacement reactions going down group 7

Reactivity decreases going down the group, and halogens become less able to gain an electron so chlorine can displace most of the halogens

What colour is Cl, Br and I in water

Cl is pale green

Br is orange

I is brown

Why is cyclohexane added to the solutions of halogen and water, what are the new colours

As iodine and bromine look very similar so add cyclohexane to differentiate them

Cl is pale green

Br is orange

I is violet

How does chlorine react with water (oxidising number)

It reacts in a disproportionate reaction where chlorine is both oxidised and reduced

Note:

Chlorine reacts in a similar way with sodium hydroxide