Question

Why is it not necessary to test the reactivity of the elemental metals with solutions of the same metal ion? To illustrate your explanation, write the equation for the potential chemical reaction using one of the metals: Cu, Zn, Mg, Ni, Pb.

Answer 1

When a metal in elemental form is placed in a solution of another metal salt it may be more energetically feasible for this "elemental metal" to exist as an ion and the "ionic metal" to exist as the element. Therefore the elemental metal will "displace" the ionic metal and the two swap places. Only a metal higher in the reactivity series will displace another. So, it is not necessary to test the reactivity of the elemental metals with solutions of the same metal ions because they will not displace each other.

For example, zinc is more active than copper and is able to displace copper ions from solution

Zn(s) + Cu ²⁺(aq) Zn²⁺(aq) + Cu(s)

Siver, on the other hand, cannot displace copper ions from solution.

Explanation

The reactivity of metals is due to the difference in stability of their electron configurations as atoms and as ions. As they are all metals they will form positive ions when they react.

Potassium has a single outer shell electron to lose to obtain a stable "Noble gas" electron configuration; the precious metals which exist in the d-block cannot form structures which are much more stable than their elemental state with the loss of just a few electrons. Metals that require the loss of only one electron to form stable ions are more reactive than similar metals which require the loss of more than one electron. Group 1A metals are the most reactive for that reason.

Metals with a greater total number of electrons tend to be more reactive as their outermost electrons (the ones which will be lost) exist further from the positive nucleus and therefore they are held less strongly.