The table shows some properties of four Group 7 elements.
| Element | Melting Point (°C) | Boiling Point (°C) | Atomic Radius (pm) |
|---|---|---|---|
| Chlorine | -101 | -34 | 99 |
| Bromine | -7 | 59 | 114 |
| Iodine | 114 | 184 | 133 |
| Astatine | 302 | 337 | 150 |
(i) State one trend in the properties of the Group 7 elements shown in the table.
(ii) Tennessine is below astatine in Group 7. Predict the boiling point of tennessine using the information in the table.
The Group 7 elements all react with Group 1 elements to form ionic compounds.
(i) Explain why the Group 7 elements all react in a similar way.
(ii) The Group 7 elements become less reactive down the group. Explain why.
(iii) Lithium reacts with bromine, Br2\text{Br}_2Br2, to make lithium bromide, LiBr\text{LiBr}LiBr. Write the balanced symbol equation for this reaction.
Sulfate ions can be identified using barium chloride solution. A student tests a compound for sulfate ions. The diagram shows the student's experiment.
The student's experiment does not work to identify sulfate ions. Explain why.