Section 2 b) Specification

2.6 describe the reactions of these elements with water and understand that the reactions provide a basis for their recognition as a family of elements

Lithium, Li: Fizzes vigorously, moves around the surface of the water.
Sodium, Na: Fizzes violently, moves quickly on the water, forms a ball shape & yellow sparks.
Potassium, K: Produces a purple flame, violently moves around the surface and pops with the force of hydrogen production.

These elements each react vigorously with cold water (due to their similar electronic configurations), an indication that they are the most reactive group of elements. They produce hydrogen gas as well as a metal hydroxide.

2.7 describe the relative reactivities of the elements in Group 1

The reactions start small at the top of the table, but gradually increase in violence as you travel down the table as the atoms are bigger and less able to hold onto their valence electron. Francium reacts extremely violently and explosively when reacting with cold water, whereas lithium just fizzes.

2.8 explain the relative reactivities of the elements in Group 1 in terms of distance between the outer electrons and the nucleus.

The elements get more reactive as you go down the group because the increase in distance between the valence electron and nucleus is increased due to increased number of shells, resulting in a weaker force of electrostatic attraction and a more reactive element.