Reactivity of Metals
Learning Objectives
The reactivity series of metals and metal displacement reactions including balanced redox equations with states indicated
Summary Notes
The Electrochemical Series
The electrochemical series is a handy tool that can be used to predict if a redox reaction will occur spontaneously.
The electrochemical series is built up by arranging various reduction reactions in order of their standard electrode potentials (redox potentials).
The standard electrode potentials of each reduction reaction is determined by calculating the potential difference between it and the standard hydrogen reference electrode, whose standard electrode potential (E°) is declared to be zero for comparison’s sake.
The most positive E° values are placed at the top of the electrochemical series.
The more positive the E° value, the less readily the element loses electrons and forms ions i.e. the more readily it is reduced.
The most negative E° values are at the bottom. The more negative the E° value, the more readily the element loses electrons and forms ions i.e. the more readily it is oxidised.
The electrochemical series can also be used to predict whether a spontaneous redox reaction will occur between chemical species if they are placed, for example, in the same beaker or test tube.
Reactivity of Metals
The most reactive metals appear at the bottom of the table since they lose electrons more easily.
The most reactive metals are the strongest reductants.
The half equations on the ECS are written in the direction in which reduction occurs.
A double arrow ⇌ is used to indicate that the reaction can proceed in both directions.
The oxidants are on the left.
The reductants are on the right.
The strongest oxidants are top left of the table.
Spontaneous Reactions
For a reaction to be spontaneous, the oxidant needs to be higher on the electrochemical series than the reductant.
Eg. Predict if the following reactions is spontaneous or not using the electrochemical series:
Zinc metal is added to a solution of silver nitrate
Practice Material
Teacher's Tip:
When faced with a redox reaction and you are required to determine the spontaneity of the reaction, identify the two reactants and circle them on the ECS. Then, draw an arrow in the direction of the reaction for both reactants. Join up the circled reactants together with a long straight line. If the shape that you have is a mirror-imaged Z, then the reaction is spontaneous.
