Chemguide: Support for CIE A level Chemistry


Learning outcome 3.1(a)

This statement deals with ionic (electrovalent) bonding.

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


You should read the page which looks at ionic (electrovalent) bonding.

The syllabus mentions calcium fluoride, which isn't covered on that page. It is exactly the same as calcium chloride except, of course, that fluorine has the inner level of 8 electrons missing.


This page actually goes beyond what this statement asks for, but you should read the whole of it. That includes the bit below the red warning notice, although you don't need to try to remember this last bit.

What is important is that you break away from any view of bonding that you may have built up at an earlier stage which over-rates the importance of noble gas structures. As the page points out, there are far more ions which don't have noble gas structures than there are which do have noble gas structures.

And I think you should at least read the last bit of that page so that you can see that the real reasons for the formation of a particular ion lie in the energetics of the process.

You will notice that the syllabus statement talks about "dot and cross diagrams", whereas there isn't a single dot and cross diagram on my Chemguide page. That's because they are a complete waste of time to draw for ionic compounds! It is much easier and quicker to write, say, 2,8,6, than to draw three circles and put the correct numbers of dots or crosses on each one.

In an exam, of course, if you are asked to show ionic bonding using dot and cross diagrams, then that is what you must do. Don't expect to get any credit for writing, for example, 2,8,6, if the question specifically asks for a dot and cross diagram.


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© Jim Clark 2010 (last modified March 2014)