To establish a reactivity series using voltage.

2Na   +   S                                 (2Na+   +   S2-)

What happens at sodium:

2Na                2Na+   +   two electrons

                              2 Na atoms      2 Na ions            given too sulphur  

What happens at sulphur:        

S   +  two electrons                    S2-   

                                 S atom    From Sodium                             S ion

          Na                                S                                 Na+                             S -        

Sodium releases its electrons better than Magnesium, this is because it depends on how tightly it is held onto by the nucleus of the atom.  This in turn also depends on how far away the electron is from the nucleus, which is what is attracting the electron, and consequently how many other electrons there are repelling it.  So the bigger the atom is the easier it is to remove the outer electron and therefore it is more reactive.  Also as there is only one on the outer shell it is repelled whereas elements like the noble gases have a full shell so it is very, very unreactive.

        

   

    Potassium                        Lithium

Prediction:

I predict that the metals will go in the following sequence:

The reason for this is the relative tendency of the metals to lose electrons.  In group one, as you go down they get more reactive, this is because the outer electron gets easier to remove.  This is because they are attracted to the positive atoms and as you go down the group the atoms get bigger.  Therefore the outer shell is further away from the nucleus.  This creates repulsion between the electrons, there is more of them as you go further down group one.  So the further down group one you go the more reactive

Say the two metals are Magnesium and copper, both in Sodium Chlorine  (this solution is used because it is full of ions and is soluble).  Magnesium is more reactive than copper, because it has a greater tendency to lose electrons into the solution, because it is a raising agent.  The experiment I do will see which metal wants to lose electrons when the metals react to form ions.  Now magnesium is more reactive so it donates the electrons to the copper so the copper becomes a metal and magnesium becomes an ion, the result is a flow of electrons through the external circuit from the magnesium electrode to the copper electrode.  This push is measured voltmeter.  The greater the push, the greater the voltage.  The greater the distance between the metals in the reactivity series, the greater the push and greater voltage.

Plan:

* Get the six metals: magnesium, zinc, aluminium and lead, copper, silver

* The magnesium is the ‘control’ metal that always stays the same, against each metal

* Set up the apparatus as shown in diagram

* Attach the positive end to zinc, aluminium, silver, lead or copper.  Also attach                           the negative end to magnesium

* Read off the voltage of the voltmeter

* Repeat experiment for each metal

Diagram:

Preliminaries:

After doing my preliminaries I decided on the following criteria:

* Wait till stable

* Repeat experiment three times and get average

* Use 20ml of solution, which will be changed every three times (every metal)

* Change magnesium every single experiment

I followed the above criteria and got many of anomalies (results for this experiment shown below) so the results where not proving my theory.

According to results above the order of reactivity is:  magnesium, zinc, aluminium, copper, lead and silver which is incorrect so I decided to redo the experiment following the following criteria:

* I am still going to wait till stable

* And also repeat experiment three times and get average

* Use 20ml of solution, which will not be changed at all through out the entire experiment

* Use same magnesium for every experiment but in between each experiment I will sand it to remove oxidation

Results:

Conclusion:

After completing the experiment I can now conclude that the reactivity series (electrochemical series) goes in the following order, the top one being the most reactive:

• Magnesium
• Aluminium
• Zinc
• Lead
• Copper
• Silver

I can also conclude that elements at the top of the reactivity series want to form positive ions and elements at the bottom of the reactivity series want to stay metals .  This makes them more stable.  To form positive ions metals must lose electrons. I can tell this is happening because as magnesium gives the other metal the electrons so the other metal becomes a metal and magnesium becomes an ion, the result is a flow of electrons through the external circuit from the magnesium electrode to the copper electrode.  So the voltmeter measures the difference, and how many electrons are being pasted between the two metals. 

An example of the donating of electrons:  

2Mg   +   Zn                                 (2Mg+   +   Zn2-)

What happens at Magnesium:

2Mg                2Mg+   +   two electrons

                              2 Mg atoms      2 Mg ions            given too Zinc  

What happens at Zinc:        

Zn +  two electrons                    Zn2-

I now also conclude that when the fizzing is taking place at magnesium the gas released is hydrogen.  This is because in the solution of Sodium- Chloride there are four elements: Hydrogen, hydroxide, sodium and chlorine.  When written as symbols they look as the following:  H+, OH-, Na+ and Cl- .  As magnesium is releasing electrons the only one that can receive the electrons is Hydrogen, and thus a gas is released.

Evaluation:

I believe our first results where insufficient to back up my prediction because we were unsure what to do.  Also we changed the magnesium every time.  The magnesium will have been various sizes and may have reacted differently each time.  Our second sets of results were a vast improvement they proved my theory.  I believe that even though these results prove my theory they are still not entirely fair.  This is because as we did the experiment I sanded the magnesium to remove any oxidation however I was not very precise and sometime removed all oxidation and other times did not.  To improve my results I could rather than sanding the magnesium, which is unreliable, I could dip the Magnesium in to a solution of Hydrochloric acid to remove the oxidation.

To gain a wider knowledge of the reactivity series I could do more metals and place them in the series.  Also I could capture the gas released and measure how much is released rather than just doing it by eye.

---