2b) Group 1 elements - lithium, sodium and potassium

2b) Group 1 elements - lithium, sodium and potassium 

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 

Group 1 elements (the alkali metals) all have one electron in their outer shell. As they are in the same group, they have similar chemical properties and will react with substances (including water) in a similar way. The Group 1 elements of lithium, sodium and potassium all react in a similar way with water, they react very vigorously which indicates that they are a family of elements and must have a similar electronic configuration. Although all the alkali metals will react similarly with water, as you go down Group 1 the elements become more reactive and will react more vigorously with water. 

Lithium: 

• Lump of lithium in water will move slowly around the surface, fizzing until it disappears. The water will become alkaline and the indicator solution will turn purple because of this. It will take approximately 30 seconds for this reaction to occur. Lithium is at the top of the group and is therefore the least reactive of all the alkali metals.

Lithium reacting with water. It will fizz like this until it disappears. 

Sodium; 

• The lump of sodium will fizz rapidly in the water and will move quickly around the surface.The indicator solution will turn purple as the water will become alkaline and it may even ignite. The time for this reaction to occur will be approximately 20 seconds. Sodium is further down in Group 1 than lithium, hence why it reacts more vigorously with the water and why it takes less time for this to happen. 

Sodium reacting with water. Having fizzed and moved quickly around the surface of the water,it has now ignited.

Potassium: 

• Lump of potassium will react vigorously with the water, and will burn with a lilac flame, or even explode. The indicator solution will again turn purple as the water has become alkaline. This reaction will occur in approximately 5 seconds. Potassium is the furthest down in Group 1 of all the three elements mentioned, hence why it reacts most vigorously with water and also why it has the quickest reaction time. 

                                                          

Potassium reacting with water. 

2.7 describe the relative reactivites of the elements in group 1

Elements in group 1 become more reactive as you go down the group. So, the least reactive metal in Group 1 is also the highest element in the group,so it would be lithium, then sodium, then potassium and so on. 

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

The further you go down Group 1, the higher the period number of each element is. While the group number stays the same, the period number will increase. This means that as you go down the group, the elements have a higher period number, meaning they have more energy levels (shells.) Because of this, the elements' outer electrons will be further away from the nucleus as you go down the group, so the element will be able to lose electrons far easier as the attraction between the outermost and the nucleus becomes less. Therefore, the outer electron will be more easily lost and the element will be more reactive as you travel down Group 1.