THE ALKALI METALS

2.6      describe the reactions of lithium, sodium and potassium with water and understand    that the reactions provide a basis for their recognition as a family of elements

Sodium, lithium and potassium all float, fizz and move around the surface when reacted with water. Sodium and potassium also melt into a ball and potassium burns with a lilac flame.

2.7      recall the relative reactivities of the elements in Group 1

Group 1 metals (aka alkali metals) are more reactive the further you go down the group.

Group 1 Metals + Water
Alkali Metal:	Hydroxide Solution Produced:	Gas Produced:	Rate of Gas Produced:
Lithium	Lithium Hydroxide	Hydrogen	Fairly Vigorous
Sodium	Sodium Hydroxide	Hydrogen	Vigorous
Potassium	Potassium Hydroxide	Hydrogen	Very Vigorous
Rubidium	Rubidium Hydroxide	Hydrogen	Explosive
Caesium	Caesium Hydroxide	Hydrogen	Extremely Explosive

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

As you go down the group the metals become more reactive. This is because their atoms get bigger, so the outer shell electrons are further away from the nucleus. This means the electrostatic forces between the nucleus and the outer shell electrons are weaker and it is easier to lose outer shell electrons. The atoms ‘want’ to lose the outer shell electrons to form full outer shells because they ‘want’ to be more stable and unreactive. Group 1 metals only have one outer shell electron to lose.

2.38i   recall simple tests for the cations Li⁺, Na⁺, K⁺, Ca²⁺ using flame tests

Metal cation:	Burns with a …
Li+	Red flame
Na+	Orange/yellow flame
K+	Lilac flame
Ca2+	Brick red flame