Question

In which of the following oxygen has +2 oxidation number?
A.${{F}_{2}}O$
B.$C{{l}_{2}}O$
C.$N{{a}_{2}}{{O}_{2}}$
D.$N{{a}_{2}}O$

Answer 1

Hint: Oxidation number of any atom is its capability to lose or gain electrons. Oxidation state of any atom is affected by the other atoms present in the molecule. Oxidation number is also affected by the electronegativity of any element.

Complete answer:
Oxidation number of any element tells us the extent up to which it can be oxidized. Oxidation number tells the capability of an atom to gain or lose electrons according to their outer shell configuration. Oxidation number has either a negative or a positive sign depending upon the nature of bonded atoms. If any element is more electronegative, then a negative sign will be attached with it, while if the element is less electronegative than the other, then a positive sign is attached with it. The oxidation number of oxygen in various compounds is usually -2, while in peroxides it is -1.
We have to find the compound in which oxygen has +2 oxidation number. Among all the given compounds, in $C{{l}_{2}}O$oxygen is more electronegative than chlorine, so it has a negative oxidation state,
Which is, oxidation state of Chlorine = -1, and oxidation state of oxygen = -2
In $N{{a}_{2}}{{O}_{2}}$ and $N{{a}_{2}}O$, oxygen will have negative oxidation state. As,
Oxidation state of Na in $N{{a}_{2}}{{O}_{2}}$, = +1, while, oxygen (peroxide) = -1 (more electronegative)
In $N{{a}_{2}}O$, Na has = +1 , while oxygen = -2 oxidation state.
In${{F}_{2}}O$, oxygen is less electronegative than fluorine, so oxygen will have a positive oxidation state. So, in ${{F}_{2}}O$oxygen will have a +2 oxidation number.
In ${{F}_{2}}O$, F = -1, while oxygen = +2 oxidation state (less electronegative)
Hence, oxygen has +2 oxidation number in ${{F}_{2}}O$.

Note:
Electronegativity of fluorine is more than oxygen, due to the smaller atomic radius of fluorine, it has less electron repulsion between the electrons which makes its tendency to attract more electrons and makes it more electronegative than oxygen. Oxygen is the second most electronegative after fluorine.