Early scientists believed that everything in the world could be simplified into four basic elements.

A tour of the Periodic Table

Later, scientists began to wonder if these four elements could be split into simpler substances.

The English scientist Henry Cavendish (1731–1810) showed that water was not an element.

He formed water by exploding a mixture of hydrogen and air with an electric spark.

The French chemist Antoine Lavoisier (1743–1794) showed that air was not an element. It could be simplified into simpler substances. He also showed that water was a compound of hydrogen and oxygen.

The electrolysis of water showed that it could be split into the two elements hydrogen and oxygen.

So, in the 18th century, scientists were discovering lots of these simple substances.

They wanted to devise a way to organise them.

They looked at the similarities and differences between the elements.

The man accredited with devising the best way of organising all of these elements was the Russian scientist, Dimitri Mendeleev, in 1869.

Properties: Extremely reactive!!!! They are stored under oil – this stops them reacting with the oxygen and water in the air.

They react violently with water, producing an alkali and hydrogen.

Group 1: The alkali metals

3LithiumLi

11SodiumNa

19Potassium

K

37RubidiumRB

55CaesiumCs

87Francium

Fr

Properties: Extremely reactive!!!!

They are soft metals – they can be cut with a knife to reveal a shiny metal. The shine disappears in seconds as the metal reacts.

The elements and their compounds burn in air, giving very colourful flames.

Group 1: The alkali metals

3LithiumLi

11SodiumNa

19Potassium

K

37RubidiumRB

55CaesiumCs

87Francium

Fr

Properties: Similar to group 1, but not as reactive.

They also react with water and oxygen, but not as violently.

Group 2: The alkaline earth metals

4BerlliumBe

12Magnesium

Mg

20CalciumCa

38Strontium

Sr

56BariumBa

88RadiumRa

Properties: Very reactive

Non-metals. Fluorine and chlorine are gases. Bromine is a liquid. Iodine is a solid.

Group 7: The halogens

9FluorineF

17ChlorineCl

35BromineBr

53IodineI

85AstatineAt

Group 8: The noble gases

Unreactive. All gases. Found in air.

2HeliumHe

10NeonNe

18ArgonAr

36KryptonKr

54XenonXe

86RadonRn

Discovered 1894: William Ramsay, Lord Rayleigh and John Strutt (London).

Why is it used in W filament lightbulbs?

Argon

Tyres of luxury cars.

Protects the rubber, from attack by oxygen, and there’s also less tyre noise.

Argon

Discovered 1868: Norman Lockyer and Edward Frankland (London).

Breathing: It raises the pitch of the voice, because sound travels faster in helium than air.

Helium

Neon

These form the large block in the middle of the table. E.g. iron, copper, lead.

The transition metals

They have a wide range of uses, e.g:

Platinum as a catalyst. Silver and gold as jewellery. Copper in wiring. Titanium in medical implants. Iron in construction.

All are solid apart from mercury.