Group 2 Elements: Redox Reactions

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The Group 2 Elements

The elements in Group 2 all have hydroxides that are alkaline, which is reflected in the common name for this group: the alkaline earth metals.

Physical Properties

The Group 2 elements have the following general properties:

they have reasonably high melting and boiling points

light metals with low densities

form colourless compounds

Electronic Configuration

The elements in Group 2 have their highest energy electrons in an s-sub shell. Together with Group 1 they form the s-block of the Periodic Table.

Each Group 2 element has:

two electrons more than the electronic configuration of a noble gas

an outer shell containing two electrons

Reactivity of Group 2 Elements

The Group 2 elements are reactive metals and strong reducing agents.

Group 2 elements are oxidised in reactions.

Each atom loses two electrons from its outer s sub-shell to form a 2+ ion: M ---> M2+ +2e-

Reactivity increases down the group, reflecting the increasing ease of losing electrons

The decrease in ionisation energies down Group 2 is an important factor in this process.

Reaction with Oxygen

The Group 2 elements react vigorously with oxygen.

this is a redox reaction

the product is an ionic oxide with the general formula MO

Calcium reacts with oxygen to form calcium oxide.

2Ca + O2 ---> 2CaO

By applying oxidation numbers to this reaction, you can identify the oxidation and reduction processes.

0 0 +2 -2

0 0 +2 -2

Calcium is oxidised and oxygen is reduced.

Reaction with Water

The Group 2 elements react with water to form hyroides with the general formula M(OH)2. Hydrogen gas is also formed.

Ca + 2H2O ---> Ca(OH)2 + H2

0 +1 +2 0

+1 0

only one H atom from each H2O has been reduced

the other H atom does not change its oxidation number

Mg reacts very slowly with water. As you move further down the group, each metal reacts more vigorously with water.

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