There is something metals have in common when they undergo chemical reaction. They have electrons in their outermost shell that they seek to get rid of.
For example, take lithium – It has 3 electrons and 1 in its outer shell:
or aluminium – It has 13 electrons and 3 in its outer shell:
There are metals that are reactive. Which mean they easily undergo chemical reaction and form new substances. An example of a reactive metal is potassium.
There are also metals that are quite unreactive. Which means they do not easily undergo chemical reaction. An example of an unreactive metal is platinum.
If we were to order metals based on how reactive they are, we would get the reactivity series.
The reactivity is in order of their reactivity. On the reactivity series list, the most reactive element is potassium and the least is platinum.