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

Outer electrons of Group 1

The electronic configuration will show the outer electrons.

Li 2.1
Na 2.8.1
K 2.8.8.1

The outer shell has only one electron in (as these elements are in group 1).
When these elements react they lose their outer electron. In order to lose an electron, the atom requires energy to overcome the electrostatic forces of attraction between the negatively charged electron and the positively charged nucleus.

K is the most reactive element of these 3 metals because less energy is required to remove the outer electron from its atom, that is required for sodium and lithium.

2.6 & 2.7 describe the reactions of these elements with water and understand that the reactions provide a basis for their recognition as a family of elements

Group 1 elements

Group 1 elements react vigorously with water to give an alkaline solution of the metal hydroxide as well as hydrogen gas. As we go down the group the elements are more reactive. 

When these elements are reacted with water, the following observations can be seen:

Lithium

• Moves around the surface of the water
• Hissing sound
• Bubbles of gas
• Gets smaller and smaller: eventually disappears

Sodium

• Moves around the surface of the water
• Hissing sound
• Bubbles of gas
• Melts into a shiny ball
• Gets smaller and smaller: eventually disappears

Potassium

• Moves around the surface of the water
• Hissing sound
• Bubbles of gas
• Melts into a shiny ball
• Burns with a lilac-coloured flame
• Gets smaller and smaller: eventually disappears

Trends show that the further down the group we get, the more reactive the elements are.