Thursday 14th June – period 3

Periodic table film

Demonstrated reaction of sodium and potassium with water.

Here is potassium – a soft metal, stored in oil

Cut to expose a shiny surface

Reacts violently with water

And leaves behind an alkaline solution

Sodium is very similar though a bit less reactive.

They are alkali metals

Reaction of magnesium with oxygen (air)

Then dissolve the oxide formed in water


This slowly produces and alkaline solution

Magnesium is an alkali earth metal


The periodic table

Elements are arranged in the periodic table in order of increasing atomic number.

Elements can be categorised as metals and non-metals.

The stepped line to the right of the periodic table separates the metals and non-metals.

In the periodic table each row is called a period and each column is called a group.

Elements in the same group tend to have similar chemical properties. Some are given names –

group 1 – alkali metals

group 2 – alkaline earth metals

group 7 – halogens

group 8 or 0 – noble gases


The transition metals are in a block in the centre of the periodic table.