Calcium and oxygen would not need to bond, they would just combine…

Calcium and oxygen would not need to bond, they would just combine, joining on to make up full shells

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. Near the end of the interview, she was asked some general questions to recap on points she had made earlier. She suggested that Ca²⁺ and O^2- would combine, but without any chemical bonding.

Could you have a double ionic bond?

(pause, c.3s)

Can you have a double bond that's ionic?

Not really sure.

If you had say, say you had calcium, two-plus (Ca²⁺), and oxygen two-minus (O^2-),

yeah,

could that form a double bond?

(pause, c.4s)

Are you not sure?

It wouldn't need to.

It wouldn't need to?

No.

Why's that?

Because one's lacking two electrons, and one's got two, so, they would just combine without needing to sort of worry about other, other erm elements.

Right so they…

Sort of joining on to make up full shells.

So they combine, but you wouldn't call that a chemical bond?

No.

From what Annie had reported earlier in the interview, she would see Ca²⁺ as a calcium atom (that's "got two" electrons in its outer shell) and O^2- as a oxygen atom (that was "lacking two electrons"), as she held an alternative conception of what was meant by the symbols used to indicate electrical charge plus and minus signs represent the charges on atoms)*.

Annie here suggests that the atoms with their charges (i.e., for Annie, deviations form full shells) would combine, and join up to obtain a full shell. From her perspective, there was no need for ionic bonding. Although Annie's notion of what was signified by the charge symbols would seem to be idiosyncratic, the idea that chemical processes occur to allow atoms to obtain full shells (the 'full shells explanatory principle') is one of the most common alternative conceptions in chemistry.