Group II Elements

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The Group II elements included in the syllabus are Magnesium(Mg), Calcium (Ca), Strontium (Sr) and Barium (Ba)

1) Reactions of elements with oxygen
Group II elements react with oxygen to form oxides

2) Reactions with water
Reactivity of group II elements with water increases down the group
Mg reacts slowly with cold water to form MgO and H2. Mg reacts rapidly with steam.
Calcium reacts steadily with water to form calcium hydroxide and hydrogen.
Strontium and barium reacts explosively with water to form hydroxides and hydrogen.

The syllabus only require students to describe the reaction. If you are interested to know why reactivity of group II elements increases down the group, chemguide.co.uk has a good explanation.

3) Behaviour of oxides with water
Reactivity of group II oxides with water increases down the group.
Group II oxides react with water to form hydroxides.

4) Thermal stability of Group II nitrates
Thermal stability of Group II nitrates increases down the group
The thermal stability of Group II nitrates can be explained in terms of the charge density of the metal cation and the polarisability of the nitrate ion.

Down the group, the ionic radii of the Group II elements increases. The charge of the metal ion remains the same, hence charge density decreases. The ion with a lower charge density is less able to polarize the nitrate ion. Hence more heat have to be supplied to decompose the nitrate to metal oxide and NO2.

5) Make predictions
There would e some questions in the exam that would require you to make some predictions. For example, thye woould say an unknown metal X is a group II element. How would its metal hydroxide react with water? So you are expected to know that it would react to form a metal hydroxide.

End of notes for Group II elements
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