Group I Properties (CIE IGCSE Chemistry: Co-ordinated Sciences (Double Award))

• The Group 1 metals are also called the alkali metals as they form alkaline solutions with high pH values when reacted with water
• Group 1 metals are lithium, sodium, potassium, rubidium, caesium and francium
• They all contain just one electron in their outer shell

Physical properties of the Group 1 metals

• The Group 1 metals:
  • Are soft and easy to cut, getting even softer and denser as you move down the Group (sodium and potassium do not follow the trend in density)
  • Have shiny silvery surfaces when freshly cut
  • Conduct heat and electricity
  • They all have low melting points and low densities compared to other metals, and the melting point decreases as you move down the Group; some would melt on a hot day

  The alkali metals lie on the far left-hand side of the Periodic Table

Chemical properties of the Group I metals

• They react readily with oxygen and water vapour in air so they are stored under oil to stop them from reacting
• Group 1 metals will react similarly with water, reacting vigorously to produce an alkaline metal hydroxide solution and hydrogen gas
• The Group 1 metals get more reactive as you look down the group, so only the first three metals are allowed in schools for demonstrations

Reactions of the Group 1 metals and water

Element	Reaction	Observations
Li	lithium  + water   →   lithium hydroxide  +  hydrogen  2Li (s)  +  2H2O (l)   →   2LiOH (aq)  +   H2 (g)	Relatively slow reaction Fizzing Lithium moves on the surface of the water
Na	sodium + water   →   sodium hydroxide  +  hydrogen  2Na (s)  +  2H2O (l)   →   2NaOH (aq)   +   H2 (g)	More vigorous fizzing  Moves rapidly on the surface of the water Dissolves quickly
K	potassium  + water   →   potassium hydroxide  +  hydrogen  2K (s)  +  2H2O (l)   →   2KOH (aq)  +   H2 (g)	Reacts more vigorously than sodium  Burns with a lilac flame  Moves very rapidly on the surface  Dissolves very quickly

Extended tier only  

• Knowing the reactions of elements at the top of the group allows you to predict the properties of other elements further down Group 1

Properties of other alkali metals (rubidium, caesium and francium)

• As the reactivity of alkali metals increases down the group, rubidium, caesium and francium will react more vigorously with air and water than lithium, sodium and potassium
• Lithium will be the least reactive metal in the group at the top, and francium will be the most reactive at the bottom
• Francium is rare and radioactive so is difficult to confirm predictions
• For example the reactions with water can be predicted:

Predicting the reaction with water

Element	Observations
Rb	Explodes with sparks
Cs	Violent explosion due to rapid production of heat and hydrogen
Fr	Too reactive to predict

• You can also look at other properties such as boiling point, melting point and density of Group 1 elements and use them to predict whether the other properties are likely to be larger or smaller going down the group