Reactivity series
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In chemistry, the reactivity series is a series of metals, in order of reactivity from highest to lowest. It is used to determine the products of Single displacement reactions.
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A reactivity series of common metals
Here a series of some of the most common metals, listed in descending order of reactivity.
| K Li Na Ca | Potassium Lithium Sodium Calcium | reacts with water and violently with acids |
| Mg Al Zn | Magnesium Aluminium Zinc | reacts with steam and acids |
| Fe | Iron | reacts reversibly with steam |
| Pb Cu | Lead Copper | no reaction with water or steam, some reaction with concentrated acids |
| Hg Ag | Mercury Silver | very small, if any, reactions |
| Pt Au | Platinum Gold | does not react with water or acids |
Sometimes H+ is placed in this series below mercury and H2O placed below iron to show which species will react with acids and water. However this is questionable as some species are "borderline" reacting only with water in certain conditions and only certain acids.
Significance
The reactivity series determines qualitatively characteristics such as the reactions with water, air and acids as demonstated above. However it is defined by the nature of the metals in single displacement reactions.
When a metal in elemental form is placed in a solution of a metal salt it may be, overall, 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 over time, thus the two swap places. Only a metal higher in the reactivity series will displace another.
Explanation
The reactivity of these metals are due to the difference in stability of their electron arrangements 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 arragement wheras the precious metals which exist in the d-block cannot form structures which are much more stable than their current state with the loss of small numbers of electrons. Metals that require the loss of single electrons to form stable ions tend to be more reactive than similar metals which require the loss of more than one electron.
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.
External links
- Science Line Chemistry (http://www.sciencenet.org.uk/database/chem/industrial/c00109b.html)