Keith S. Taber
Annie was a participant in the Understanding Chemical Bonding project. She was interviewed near the start of her college 'A level' course (equivalent to Y12 of the English school system). Annie was shown, and asked about, a sequence of images representing atoms, molecules and other sub-microscopic structures of the kinds commonly used in chemistry teaching. She was shown a representation of the resonance between two canonical forms of the ethanoate ion, sometimes used to imply the delocalisation of the ionic charge across the COO- grouping.
Any idea what this is?
They're organic compounds. And one's an inversion of the other.
Any idea what that arrow means in the centre of the page?
Does it mean that if you turned either of the, the O-minus, or the O that's double bonded around then you'd get the other compound? And it's exactly the same for that one if you turn that around, and you'd get, so it's like a reversible (pause, c4.s) thing.
Now what did you say about double bonded, what's this about being double bonded?
The oxygen is joined on the carbon with double bonds.
So what's a double bond? Is that, is that, you talked about covalent bonds earlier. Is a double bond the same as a covalent bond, or different to a covalent bond or?
Different.
So are there any covalent bonds, – the top one for example – are there any covalent bonds there?
Yeah.
How many covalent bonds are there?
Five.
And how many double bonds?
One.
And are there any ionic, ionic bonds?
No.
So we've got five covalent and one double.
Yeah.
Annie recognised the presence of a double bond (C=O) in the canonical forms shown, but seemed to see 'double bond' as an additional category of chemical bonding, different to covalent bonding, rather than referring to a particular type of covalent bond. So for Annie, each canonical form contained five covalent bonds (3H-C, C-C, C-O) and one double bond (C=O).
As the interview proceeded, Annie also suggested that single bonds are different to covalent bonds or ionic bonds.
