Video Transcript
Consider the reaction between
sodium and chlorine: Cl2 gas plus two Na solid react to produce two NaCl solid. Which chemical species is oxidized
in the reaction? (A) The sodium atoms, (B) the
sodium ions, (C) the chlorine atoms, or (D) the chlorine ions.
If a chemical species has been
oxidized, it means it has undergone oxidization, where oxidization is a reaction
that involves the loss of electrons from a substance. Since we want to find out which
species has been oxidized, we want to find out which species has lost electrons. Our starting materials are chlorine
and sodium in their elemental form. Neither of these species are
charged. The product is sodium chloride,
commonly known as salt. It is an ionic species made of
sodium ions and chloride ions. More specifically, the ions are Na+
and Cl−.
Chlorine started out as an
uncharged species. But upon reaction with sodium, it
became negatively charged. This means that chlorine gained
electrons. Therefore, chlorine has not
undergone oxidization; it has undergone reduction. Reduction can be defined as a
reaction that involves the gain of electrons in a substance. Sodium, on the other hand, existed
as a neutral starting material. But in the product, it is
positively charged. Sodium atoms have to lose electrons
to become positively charged sodium ions. So the sodium atoms undergo
oxidization and are therefore oxidized.
So the answer to the question
“Which chemical species is oxidized in the reaction?” is (A) the sodium atoms.
