6.1 Group 1

Question 1

Physical properties in group 1

Answer 1

The group 1 metals are known as the alkali metals.
They form alkaline solutions when they react with water.
The group 1 metals are lithium, sodium, potassium, rubidium, caesium and francium and they are found in the first column of the periodic table.
They are all soft metals which can easily be cut with a knife.
They have relatively low densities and low melting points.
They are very reactive (they only need to lose one electron to become highly stable) .

Question 2

How Alkali Metals React with Water

Answer 2

group 1 metal + water ⟶ metal hydroxide + hydrogen
2M (s) + 2H2O (l) ⟶ 2MOH (aq) + H2 (g)

They form an alkali solution when they react with water which is caused by the hydroxide and hydrogen gas is given off.
Effervescence can be observed as well as a coloured flame (exothermic reaction).
lithium - red flame
sodium - orange flame
potassium - lilac flame
rubidium - red-violet flame
caesium - blue-violet flame

Question 3

Trends in group 1

Answer 3

More reactive as you go down the group.
Vigorous reactions with water and oxygen so stored in oil.
Melting point decreases as you go down the group.
All have low densities and are soft.

Question 4

Melting and boiling point of group 1

Answer 4

Low melting points that decrease as you go down the group. this is because the metal ions get larger as you go down group 1 so the attraction between the delocalised electrons and metal ions are weaker so the metallic bonds are also weaker.

Question 5

Reactivity of group 1

Answer 5

The reactivity of the group 1 metals increases as you go down the group.
When a group 1 element reacts its atoms only need to lose electron to gain a full outer shell to become stable.
When this happens, 1+ ions are formed.
As you go down group 1, the number of shells of electrons increases by 1.
This means that the outermost electron gets further away from the nucleus, so there are weaker forces of attraction between the outermost electron and the nucleus.
Less energy is required to overcome the force of attraction as it gets weaker, so the outer electron is lost more easily.