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# 2.1.1 The alkali metals and the noble gases.

The alkali metals are the elements lithium, sodium, potassium, rubidium, caesium and francium. They are grouped together because they all behave similarly (except with different ferocity) and together form Group 1 of the periodic table.

They are all in fact very soft metals that can be cut with a knife and have relatively low melting temperatures. They do not occur naturally because they react readily with air and moisture and so need to be stored under oil.

One of the signature reactions of alkali metals is their reaction with water in the following video.

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Transcript

How does the reactivity with water vary on going from lithium to caesium?

### Answer

The reaction becomes progressively more vigorous (and spectacular).

At the opposite end of the scale are the noble gases.

These are found in the last column on the right of the periodic table, and are present in the atmosphere in small amounts:

- 0.934% argon
- 0.0018% neon
- 0.00052% helium
- 0.00011% krypton
- 0.000009% xenon

The noble gases are all characterised by being extremely unreactive (in fact they are often called the inert gases). This is illustrated in the following video clip.

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Video: noble gases
Transcript
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