Group 1 - Alkali metals

Group 1 metals are known as the 'alkali metals'. Group 1 metals include lithium, sodium and potassium. 

As you go down group 1, the alkali metals become more reactive - the outer electron is more easily lost because it's further away from the nucleus (the atomic radius is larger) so less energy is needed to remove it. 

They all have the following physical properties: Low melting point and boiling point (compared to other metals) Low density - lithium , sodium and potassium float on water Very soft - they can be cut with a knife

When lithium, sodium and potassium are put in water they react very vigorously. They move around the surface, fizzing furiously and produce hydrogen.The reactivity with water increases down the group - the reaction with potassium gets hot enough to ignite it. Sodium and potassium melt in the heat of the reaction. An alkali forms which is the hydroxide of the metal.

Alkali metal compounds burn with characteristic colours:- Dip a wire loop into some hydrochloric acid to clean and moisten it. Put the loop into a powdered  sample of the compound to be tested, then place the end in a blue Bunsen flame Alkali metal ions will give pretty coloured flames - the colour of the flame tells you which alkali metal is present.

Lithium: Red flameSodium: Yellow/orange flamePotassium: Lilac flame

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