Difference Between Reactivity Series And Electrochemical Series

Reactivity And Electrochemical Series - Metals

The reactivity series can be used to compare the relative reactivities of different metals. It lists metals in order of general chemical reactivity. Metals generally react by losing electrons to form positive ions. The more readily a metal loses electrons, the more reactive it is – and the greater its strength as a reductant. Metals higher up in the series can reduce the ions of those lower down.

The standard electrode potential of a metal also indicates its strength as a reductant. The more negative the value of the standard electrode potential of a metal, the greater is its strength as a reductant. Hence, you might expect the metal reactivity series and standard electrode potentials to list metals in the same order. However, you must remember that the metal reactivity series is based on observing a range of reactions, such as displacement reactions between solid metals and solid metal oxides. Standard electrode potentials refer specifically to reactions taking place in aqueous solution.

Below is a comparison of the reactivity series with the electrochemical series, which ranks metals according to their standard electrode potentials.

The obvious discrepancy is the relative positions of sodium and calcium. Calcium is a stronger reductant than sodium according to Eo (standard electrode potential) values, but the metal reactivity series suggests that calcium is less reactive than sodium. This discrepancy arises because calcium reacts at a much slower rate, in displacement reactions for example, which in turn happens because two electrons must be removed, not one as for sodium.

Note also that aluminium reacts readily with oxygen in the air, forming a layer of stable aluminium oxide on its surface. This impervious oxide coat often causes aluminium to exhibit lower reactivity than its position in the metal reactivity series indicates.

Group IV Elements - CAPE Chemistry Unit 1

Elements - Structure And Bonding

Main Points To Be Used In Answering A Past Paper Question:

• Down the group there is a change in structure from giant molecular to giant metallic and a change in bonding from covalent to metallic.
• From C to Ge elements exhibit a giant molecular structure.
• Sn and Pb exhibit a giant metallic lattice structure.
• From C to Ge bond length between group IV atoms increases and bond energy/strength decreases.

Elements - Electrical Conductivity

Trend: Going down the group there is a general increase in electrical conductivity.

Reason: Down the group there is a gradual increase in metallic character due to an increase in delocalisation of electrons throughout the structure.

Note: There is an increase in electrical conductivity from C(diamond) to Sn. There is a decrease from Sn to Pb which has never been addressed in the past papers. Hence we use the phrase "general increase" when talking about the trend in electrical conductivity down the group.