How would you define oxidation and reduction in terms of electron transfer?
Oxidation is the taking away of electron from one atom
Reduction is addition of an electron to one atom
The electron transfer of an electron from a reducing agent like sodium to an oxidizing agent like oxygen results in an electron being transferred (taken away )from the sodium) and an electron being transferred ( added) to the Oxygen)
The result is Sodium ends up with a loss of electron density and a positive charge. Oxygen ends up with the gain of electron density and a negative charge.