Chemguide: Support for CIE A level Chemistry


Learning outcome 10.1(a)

This statement wants you to be able to describe the reactions between the Group 2 elements and oxygen, water and dilute acids.

Before you go on, you should find and read the statements in your copy of the syllabus.


Reactions with oxygen

You will find these discussed on the page reactions of the group 2 elements with air or oxygen.

That page includes more information than you need.

  • First of all, notice that the syllabus talks about the reaction with oxygen - not with air. That means that you can ignore any mentions of the reactions with nitrogen.

  • Secondly, notice that the syllabus, under "Content", only wants the reactions of the elements from magnesium to barium. Beryllium isn't mentioned. It is possible for the examiners to ask you to predict some properties of beryllium (or of radium at the bottom of the group) in statement 10.1(d), but we will deal with that problem on the page about 10.1(d) later.

  • This syllabus statement just says "describe" - not "describe and explain". All you need are simple descriptions and equations.

  • The syllabus section on Periodicity (Section 9) doesn't expect you to know about the formation of peroxides. However, CIE have asked a multiple-choice question about the structure of the peroxide ion in barium peroxide. For safety, you should be aware of the formation of peroxides by strontium and barium as described on the Chemguide page. You need to realise that the peroxide ion carries a single negative charge on both oxygen atoms. You will find a diagram of that in the Explanations section of that page.


Important update September 2014:  CIE have been asking multi-choice questions (most recently in June 2014 Paper 12 Q12 and Paper 13 Q19) about what colour flame Group 2 metals burn with. The choices included (amongst others) green or white for barium, and red or white for strontium.

If you have read my Chemguide page about this, you will know that I describe both of these flames as white with some coloured tinges. In other words both "white" and a colour are parts of the description of the flame. I see these questions as being invalid, and impossible to answer for anyone who has actually seen these metals burning rather than reading about them.

For CIE exam purposes, you must therefore choose the flame test colour for burning the metals calcium (red), strontium (red) and barium (green). There is obviously no problem with magnesium (white)!




Reactions with water

You will find these discussed on the page reactions of the group 2 elements with water.

For this statement, all you need to know are the descriptions - particularly for magnesium and calcium, which seem to be what are mainly asked in exams. The reactions for strontium and barium will look similar to calcium, but with faster reactions.

The explanations will come later in statement 10.1(d).


Reactions with dilute acids

You will find these discussed on the page reactions of the group 2 elements with acids.

You can ignore the references to beryllium, especially with nitric acid. You can also ignore references to anything other than dilute acids.


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© Jim Clark 2012 (last modified September 2014)