The activity series of metals or reactivity series is a list of metals from most reactive to least reactive. Knowing the activity series helps you predict whether or not a chemical reaction occurs. Specifically, use it for identifying whether a metal reacts with water or acid or whether it replaces another metal in a reaction. Replacement reactions and ore extraction are two key uses of the activity series.
Activity Series of Metals Chart
Here is an activity series chart for metals around room temperature.
| Metals (most to least reactive) | Reaction |
|---|---|
| Cesium (Cs) Francium (Fr) Rubidium (Rb) Potassium (K) Sodium (Na) Lithium (Li) Barium (Ba) Radium (Ra) Strontium (Sr) Calcium (Ca) | Reacts with cold water, replacing hydrogen and forming hydroxide |
| Magnesium (Mg) | Reacts very slowly with cold water, but vigorously with acids, forming hydroxides |
| Beryllium (Be) Aluminum (Al) Titanium (Ti) Manganese (Mn) Zinc (Zn) Chromium (Cr) Iron (Fe) Cadmium (Cd) Cobalt (Co) Nickel (Ni) Tin (Sn) Lead (Pb) | Reacts with acids, generally forming oxides |
| H2 | For comparison |
| Antimony (Sb) Bismuth (Bi) Copper (Cu) Tungsten (W) Mercury (Hg) Silver (Ag) Gold (Au) Platinum (Pt) | Highly unreactive (Sb reacts with some oxidizing acids) |
If you look around, you’ll notice charts from different sources may order the elements slightly differently. For example, in some charts, you’ll find sodium listed as more reactive than potassium. This is because the conditions of a proposed reaction matter. The order of the metals in the table comes from experimental data on a metal’s ability to displace hydrogen from water and acid. Particular metals react more with one acid than another, plus temperature plays a role.
What’s important is keeping in mind the general trends. Alkali metals are more reactive than alkaline earths, which in turn are more reactive than transition metals. Noble metals are the least reactive.
The alkali metals, barium, radium, strontium, and calcium react with cold water. Magnesium only slowly reacts with cold water, but rapidly reacts with boiling water or acids. Beryllium and aluminum react with steam or acids. Titanium only reacted with concentrated mineral acids. Most transition metals react with acids, but do not react with steam. The noble metals only react with powerful oxidizers, such as aqua regia.
Most Reactive and Least Reactive Metals
From the table, note that the most reactive metal on the periodic table is cesium. The least reactive metal is platinum.
How to Use the Metal Activity Series – Example Problems
So, a metal that is higher on the activity series replaces one lower on the series. It does not replace a metal higher on the series. When one metal replaces another it displaces it in replacement reactions and also displaces ions in aqueous solution.
For example, adding zinc metal to an aqueous solution of copper ions results in precipitation of copper:
Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)
This occurs because zinc is more reactive than copper and is higher on the activity series. However, if you add silver metal to an aqueous copper solution, nothing changes. Silver is below copper on the activity series so no chemical reaction occurs.
However, some metals don’t displace hydrogen from water. Metals lower on the activity series react with acids. For example, zinc displaces hydrogen from sulfuric acid:
Zn(s)+H2SO4(aq) → ZnSO4(aq)+H2(g)
Now, let’s apply this information to potential chemistry problems:
Example #1
Will the following reaction occur?
Mg(s)+CuCl2(aq)→MgCl2(aq)+Cu(s)
Magnesium is higher on the activity series than copper, so it replaces it in reactions. Yes, this reaction will occur.
Example #2
What happens when you place a chunk of zinc into a container of hydrochloric acid?
From the activity series you know that zinc displaces hydrogen from acid. Hydrochloric acid is actually an aqueous solution of HCl, so you don’t get zinc chloride. Here is the reaction:
Zn(s) + 2 HCl(aq) → Zn2+(aq) + 2 Cl–(aq) + H2(g)
Example #3
What happens when you place a chunk of copper into hydrochloric acid?
From the reactivity series, you know copper is pretty unreactive. No reaction occurs. Nothing happens.
Understanding Reactivity
The reason some metals are more reactive than others has to do with their electron configuration. Alkali metals readily lose their single valence electron and gain stability. Meanwhile, noble metals are d-block elements that require the loss or gain of several electrons to reach a noble gas configuration.
Usually, the metal with more electrons is more reactive than the one with fewer electrons. This is because metals with more electrons have electron shells that are further away from the nucleus, so their electrons are not as tightly bound.
References
- Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 82–87. ISBN 0-08-022057-6.
- Wah, Lim Eng (2007). Longman Pocket Study Guide ‘O’ Level Science-Chemistry (2nd ed.). Pearson Education. ISBN-10: 981-06-0007-0.
- Wolters, L. P.; Bickelhaupt, F. M. (2015). “The activation strain model and molecular orbital theory”. Wiley Interdisciplinary Reviews: Computational Molecular Science. 5 (4): 324–343. doi:10.1002/wcms.1221
- Wulfsberg, Gary (2000). Inorganic Chemistry. University Science Books. ISBN 9781891389016.