What makes the halogens so reactive? 

Write a word equation for the reaction of bromine with potassium iodide. What do you expect to see? 

Explain why the following reaction occurs.

${\mathrm{Br}}_2 + 2\mathrm{KI} \to 2\mathrm{KBr} + {\mathrm{I}}_2$

The fifth element in Group $\mathrm{Vll}$ is called astatine. It is a very rare element. Do you expect it to be a gas, a liquid, or a solid? Give your reason.

The fifth element in Group $\mathrm{Vll}$ is called astatine. It is a very rare element. Do you expect it to be harmful or harmless?