# 5.1: Activity Series

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Learning Objectives

• Define activity and determine which element in a reaction is more active given the balanced chemical equation

• Write an activity series for 3 or more elements based on a multiple replacement reactions.

## Activity Series

Groups, IA, IIA, and IIIA tend to lose electrons.  Transition elements tend to lose electrons too, but are more difficult to predict.  Some elements lose their electrons more easily than others.

Activity is the ability of an element to lose electrons (oxidize).  Notice that this is the opposite of electronegativity which is a value associated with how easily an element gains electrons.

Activity series list elements according to how easily they lose electrons.

Figure $$\PageIndex{1}$$, provides an example of an activity series.

example:  Zn and Cu both tend to lose 2 electrons, but the zinc wants to lose them more, so much so that it can force the two electrons on Cu2+ and make it become Cu again.

Zn  +  Cu2+            →       Zn2+  +    Cu

We say that Zn is more active than the copper.  Positive ions (cations) can't just be floating around by themselves in solution, they have to have a negative ion (anion) to balance them.  In the equation below, nitrate is there to balance the charges.

Zn +  Cu(NO3)         →             Zn(NO3)2  +  Cu

Nitrate ion in both the reactants and the products has a -1 charge.  When an ion keeps the same charge in a reaction and is just there to balance out the opposite charges, we call it a Spectator Ion.

Suppose a piece of copper was placed in a solution of SnCl2, and nothing happens.  In this case the tin is more active than the copper, as the copper is not able to force its electrons onto the tin.

Cu  +  SnCl2   →             NR

If a piece of zinc is placed in the SnCl2 a reaction occurs.

Zn  + SnCl2     →          Zn Cl2  + Sn

Using all three of the reactions above, we can make an activity series for Cu, Zn, and Tin.  In the first reaction we determined that zinc is more active than copper and the third reaction shows us that zinc is also more active than tin.  Therefore zinc is the most active metal.  The second equation shows us that tin is more active then copper.  Basined on this information, an activity series for these three metals would be:

Zn                                        Sn                                                        Cu

most active                                                                                 least active

## Metals and Acid

Acids lose H+ ions when in solution.  If you place a metal  that is more active than the H+ in an acid the metal will force the electrons onto the hydrogen ion.  The Hydrogen ions then link up and form hydrogen gas, H2.  When conducting such an experiment the H2 appears as bubbles.

Mg  +  2HCl                    MgCl2   +  H2

Is the Mg higher or lower in activity than hydrogen?

Mg is higher in activity than H+

## Writing Equations to Make an activity Series

Notice that all of the above equations are displacement reactions.  Regardless of what the description of the reaction, the equation will always be a single or double displacement reaction which we learned about in Unit 4.  Let's review the steps to writing displacement reactions.

1. Figure out what the reactants and products will be.
• The cations will switch places in the products for double replacement reactions.
• The element will replace the cation in the reacting compound and result in a new product for single replacement reactions.
2. Make sure that all of the compound formulas are correctly written based on the oxidation state of the elements involved.
3. Balance the equation.

5.1: Activity Series is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.