This question is about the trends and properties of elements in Groups 1, 7, and 0.
Potassium is a Group 1 alkali metal.
A technician carefully adds a small piece of potassium to a trough of water. The potassium reacts vigorously and moves very rapidly across the surface of the water.
Describe two other observations you would make.
Reactivity increases going down Group 1 from lithium to caesium.
Explain this trend in reactivity.
Use ideas about the electronic configurations of the atoms in your answer.
Look at the table. It shows information about some Group 7 elements.
Complete the gaps (i), (ii), and (iii) in the table.
| Element | Formula | Colour | State at room temperature |
|---|---|---|---|
| Fluorine | (i) ...................... | pale yellow | gas |
| Chlorine | Cl2\text{Cl}_2Cl2 | (ii) ...................... | gas |
| Bromine | Br2\text{Br}_2Br2 | red-brown | liquid |
| Iodine | I2\text{I}_2I2 | grey-black | (iii) ...................... |
Fluorine boils at −188 ∘C-188\text{ }^\circ\text{C}−188 ∘C.
Explain why fluorine has a low boiling point.
Argon and krypton are elements in Group 0 (the noble gases) and are extremely unreactive.
Explain why, in terms of their electronic configurations.