Question

Name the compound that gets oxidized in the following reaction: $4Na+{{O}_{2}}\xrightarrow{{}}2N{{a}_{2}}O$

Answer 1

We know that Generally the compound whose oxidation number increases during the reaction is known as oxidized compound and the compound whose oxidation number decreases during the reaction is known as reduced compound.

Complete answer:
Let us first talk about the oxidations number of elements in the compounds given in the reaction. Oxidation number of an element: It is defined as the total number of electrons that an atom accepts or loses in order to make a chemical bond which results in the formation of a chemical compound.
Oxidation: The compound which loses the electron during the reaction or the compound whose oxidation number increases during the reaction.
Reduction: The compound which gains the electron during the reaction or the compound whose oxidation number decreases during the reaction.
Sodium atom to sodium ion: oxidation, e loss, ox. state change is from $0$ to $+1.$
$2~\times ~Na~$increases, each from $\left( 0 \right)~$ to $\left( +1 \right),$ losing one electron per Na atom, which is 'electronically' balanced by the oxygen molecule to peroxide ion: reduction, e gain, ox. state change $2~\times ~O~$ decreases, each from $\left( 0 \right)$ to $\left( 1 \right),$ gaining two electrons per O atom (or two electrons per ${{O}_{2}}$ ​ molecule), and the half reactions are:
oxidation: $Na~\to ~~N{{a}^{+}}+{{e}^{-}}$(formation of sodium ion).
reduction: ${{O}_{2}}+2{{e}^{-}}\xrightarrow{{}}O_{2}^{-}$ (formation of the peroxide ion).
Adding and balancing $2\times \left( i \right)+\left( ii \right)$gives the full equation, $4Na{{~}_{\left( s \right)}}+~{{O}_{2\left( g \right)}}~\to ~2N{{a}_{2}}{{O}_{\left( s \right)}}$
Therefore, Sodium $(Na)$is oxidised as it gains oxygen and oxygen gets reduced.

Note:
Remember that Generally the compound which is oxidised in the reaction will act as reducing reagent (which oxidises the other compounds) and the compound which is reduced in the reaction will act as oxidising reagent (which reduces the other compounds) for the reaction.