Question

why can not each metal react with its own salt ?

Answer 1

in a displacement reaction a more reactive metal displaces the less reactive metal from it's salt solution. The reaction is often known as metal displacement reaction.the elements potassium,sodium,lithium and calcium are very reactive and they react with cold water to
produce hydroxides and hydrogen gas

hope it helps!

Answer 2

Sodium as an element is looking to donate one of its electrons to achieve a stable outer electron configuration. When it reacts with chlorine, the chlorine takes that electron and it is happy since it has a stable electron configuration and the sodium is happy since it has a stable electron configuration. In that exchange of an electron, the sodium becomes positive since it has given its electron to the chlorine, and the chlorine now has a negative charge since it has an extra electron. And both are now ions.

As an ion, sodium doesn't want to gain or lose any more electrons, so it isn't going to react with anything, including water. It has already reacted.

Now , this is an example of a sodium. This will be the same answer for anything.