Chemistry · Oct / Nov 2017 · Paper 11 · Question 9

When a piece of sodium is heated in air, it reacts with oxygen to form the ionic compound sodium oxide, Na$_2$O. In terms of electrons, which statement correctly explains what happens when sodium reacts with oxygen?

1. AAn oxygen atom shares two electrons with two sodium atoms.
2. BA sodium atom loses two electrons which are transferred to an oxygen atom.
3. CA sodium atom shares its outer shell electron with two oxygen atoms.
4. DTwo sodium atoms each lose one electron which are both transferred to one oxygen atom.

As printed in the paper