Final answer:
The formation of a sodium ion from a sodium atom is oxidation because the sodium atom loses an electron, which increases its oxidation state from 0 to +1 in this redox reaction.
Step-by-step explanation:
The formation of a sodium ion from a sodium atom is an example of oxidation because the sodium atom loses an electron during the process. In an oxidation-reduction (redox) reaction, oxidation refers to the loss of electrons, which increases the oxidation state of an element.
When metallic sodium reacts with chlorine gas to form sodium chloride, each sodium atom loses one electron and becomes a sodium ion with a +1 charge, illustrating the concept of oxidation.
For instance, in the reaction 2 Na + Br₂ → 2 NaBr, sodium is oxidized because it loses an electron to become Na+ with an oxidation state of +1. Similarly, when sodium metal reacts with oxygen, sodium is oxidized to form sodium oxide, with the sodium atoms losing electrons to the oxygen atoms. In both cases, the changing oxidation numbers signify that a redox reaction has occurred.