Chemguide: Support for CIE A level Chemistry

Learning outcome 3.2

Ionic bonding

This statement looks at ionic (electrovalent) bonding.

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

Learning outcomes 3.2.1 and 3.2.2

Statement 3.2.1 is particularly important because it defines ionic bonding. Make a note of it.

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.

Looking ahead, statement 3.7 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.

You might have to draw dot-and-cross diagrams for the atoms before transfer of electrons and for the ions after transfer with arrows showing the transfer. This would be really tedious for any atoms with more than a couple of shells.

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© Jim Clark 2019