The Activity Series (A Pecking Order for Metals)

When we react metals with oxygen and water we start to see a pattern:

Metal / Reaction with Oxygen / Reaction with Water / Reactions with Acid / Activity
Li / React very quickly
when heated, giving
out a bright light / React vigorously
in cold water (CW) / Most active
(prefer to be ions)
Increasing
activity
Least active
(prefer to be atoms)
Ca
Mg / Reacts slowly in CW,
faster in steam
Al / React more
slowly, powders
burn easily
Zn / Require strong
heating in steam
Fe
Pb / Surface only reacts, slowly dulls in air / No reaction, even if
heated in steam
Cu

This order of metals is called the activity series. Remember, aluminium needs to have its oxide coating removed before it will show its true place in the series.

Note: 1. The metals at the top react readily & rapidly

2.  Metals in the middle react less readily, some heat may be needed

3.  Metals at the bottom react slowly, if at all.

We can also see these differences in the metals around us. Gold bracelets in tombs thousands of years old are as smooth and bright as ones made today – the gold has not reacted to form compounds. Yet the iron of car bodies rusts away in a decade or two unless specially protected – it reacts quickly with water and oxygen to form hydrated iron oxide. Mercury can be made by heating mercuric oxide in air and lead forms when lead oxide is heated strongly with carbon. But sodium can’t be made this way – it must be made by electrolysis of molten sodium chloride. Clearly metals are different.

Metal compounds are ionic: the metal atoms lose electrons to form positive ions which are arranged in a regular pattern with negative ions. When metals are made from their compounds, the positive metal ions must take back electrons to become atoms again. If a metal is easy to form from its compounds, then it must be easy to get the metal ion to gain electrons. If it is difficult to get the metal ion to gain electrons then the metal will be difficult to form from its compounds.

Metals which form easily tend to be unreactive, because if a metal ion gains electrons easily, the metal atom is reluctant to lose them. Likewise, if it was hard to make a metal ions gain electrons then it is easy to make the metal atom lose them again.

So, if M+ + e- à M is easy, then M - e- à M+ is hard

Some metals prefer to be atoms, and they tend to be unreactive, e.g. gold, mercury. Other metals prefer to be ions and they tend to be very reactive- these are the metals that are mined as compounds.

Questions

1. Copy the table, leaving the 4th column blank for acids (we will fill this in after we do the acids

topic, later in the year).

2. Copy & complete these statements:-

A.  The higher a metal in the activity series the ______likely it is to react with other substances.

B.  The metals at the top of the activity series come from group _____ of the periodic table. The next metals come from group ____, then group ______. The last few come from the group called the______metals.

C.  The elements _____ and _____ tend to be found as metals in the earth’s crust, but elements such as _____ and ____ are only ever found as compounds in the ground & in the sea.

3. A. Explain where you would expect to find Na if we were to put it in this activity series.

B. Explain where you would expect to find Au & Ag if we were to put them in this activity series.

4. Explain why magnesium reacts more vigorously with:-

A.  oxygen than with air.

B.  steam than with water.

5. Why is lithium stored in oil?

6. Write word equations and then balanced equations for the following:-

A.  potassium and water

B.  lithium and oxygen

7. Which metals would you expect:-

A.  to react rapidly in acids?

B.  to react rather slowly in acids?

C.  to not react at all with acids?

8. X is a metal that reacts with steam to form hydrogen and a white insoluble oxide. Metal X does

not react with cold water. Name 2 metals X could be.

9.  A student is given two samples of grey metal powders in unlabelled jars. One is zinc & the

other magnesium. Explain how the student could work out which metal was in which jar.

10. Describe the reaction that could occur if water was sprayed onto burning aluminium metal.

11. The wooden hull of sailing ships did not use to last very long as it was attacked by marine

worms. This was prevented by covering the hull in a sheath of metal that was not attacked by

seawater. What metal would be suitable?

12.  Explain why early people on earth discovered copper, gold & silver long before they knew of other metals.

13.  Try to make up a mnemonic to help you remember the order of metals in the activity series.

Note:

For the chemical properties of metals you need to know:-

·  the strength of the reaction of each metal with oxygen, water (& later, acids)

·  the appearance and name of the products (& be able to give an equation)

·  the order of the metals in the activity series