By reacting metals with oxygen, acids and water, scientists have been able to construct a table of metals, listing them in order from the most to the least reactive.
This table is called the reactivity series:
The metals at the top are so reactive that they can even set on fire or explode when stored in water. They also tarnish (go dull) very quickly when exposed to air.
The picture below shows the explosive reaction produced when potassium is placed in water:
Metals near the bottom of the series are unreactive. Platinum, for example, will not corrode in air or react with acids. This makes it an ideal metal to make jewellery from as it will not tarnish or be damaged by chemicals.
The picture below shows jewellery made from platinum.
The reactivity series may seem complicated, but there is an easy way to remember it, using this simple pneumonic (or you can make up your own!).
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