Group VII properties
Group VII — the halogens
- Chlorine, bromine, iodine are diatomic non-metals (e.g. $\text{Cl}_2$).
| Halogen | Appearance at r.t.p. |
|---|---|
| chlorine | pale yellow-green gas |
| bromine | red-brown liquid |
| iodine | grey-black solid |
- Going down: density increases, but reactivity decreases (opposite to Group I).
Practice
Match each halogen to its appearance at room temperature.
Down the group they go gas → liquid → solid as melting/boiling points rise.
Practice
Going down Group VII, reactivity:
Halogen reactivity decreases down the group — the opposite of Group I.
Displacement reactions
- A more reactive halogen displaces a less reactive halide from solution.
- Chlorine displaces bromine from potassium bromide:
$$\text{Cl}_2 + 2\text{KBr} \rightarrow 2\text{KCl} + \text{Br}_2$$
Practice
Chlorine displaces bromine from potassium bromide because chlorine is:
A more reactive halogen displaces a less reactive halide ion from its solution.
You've got it
Key idea
- Group VII = halogens, diatomic non-metals; chlorine (gas) → bromine (liquid) → iodine (solid)
- reactivity decreases down the group (opposite to Group I)
- a more reactive halogen displaces a less reactive one: $\text{Cl}_2 + 2\text{KBr} \rightarrow 2\text{KCl} + \text{Br}_2$