Oxygen is a p block element. It shows -2 number commonly.
It shows some oxidation numbers. Generally it shows +4 oxidation numbers.
The sum of the oxidation numbers is zero for the compound.
0 in the elemental form, +2 and +4 in its compounds
Argon is very unreactive as it is a noble gas. Its common oxidation number is zero.
It is a gas. Generally it shows -2 oxidation number.
The oxidation number for NO3 is -1. Since oxygen is usually assigned an oxidation number of -2 in compounds, the total oxidation number for the nitrate ion (NO3) must be -1 to account for the three oxygens.
The oxidation number for Pb in PbO2 is +4. Oxygen in compounds is typically -2, so with two oxygens, the total oxidation number contributed by oxygen is -4. This means that the oxidation number of Pb must be +4 to balance the charges.
The oxidation state of carbon in ethanal (C2H4O) is +2, as it is bonded to two more electronegative oxygens. The oxidation state of oxygen is -2, while the hydrogen atoms have an oxidation state of +1.
-1 in bromide (most common). It can exhibit oxidation numbers from -1 to +7 (in HBrO4)
Argon doesn't form compounds and so its oxidation number is zero
-1 is most common in chlorides. However chlorine can exhibit oxidation numbers up to +7 in its compounds.
The most common oxidation numbers of fermium, Fm, are +2 and +3, though there are no stable isotopes (half-life times shorter than 100 days)